feat(09-01): rework frequency picker with shortcut chips and freeform picker

- Replace 10-chip grid + hidden Custom mode with 4 shortcut chips (Täglich, Wöchentlich, Alle 2 Wochen, Monatlich)
- Always-visible freeform 'Alle [N] [Tage/Wochen/Monate]' picker row below chips
- Bidirectional sync: tapping chip populates picker; editing picker recalculates chip highlight
- _resolveFrequency() now reads exclusively from picker (single source of truth)
- Edit mode correctly loads all 8 IntervalType values including quarterly and yearly
- Add l10n keys frequencyShortcutDaily/Weekly/Biweekly/Monthly to app_de.arb

lib/features/tasks/presentation/task_form_screen.dart

@@ -32,11 +32,10 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
   final _formKey = GlobalKey<FormState>();
   final _nameController = TextEditingController();
   final _descriptionController = TextEditingController();
-  final _customIntervalController = TextEditingController(text: '2');
+  final _customIntervalController = TextEditingController(text: '1');
 
-  FrequencyInterval? _selectedPreset;
+  _ShortcutFrequency? _activeShortcut;
-  bool _isCustomFrequency = false;
+  _CustomUnit _customUnit = _CustomUnit.weeks;
-  _CustomUnit _customUnit = _CustomUnit.days;
   EffortLevel _effortLevel = EffortLevel.medium;
   DateTime _dueDate = DateTime.now();
   Task? _existingTask;
@@ -45,7 +44,9 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
   @override
   void initState() {
     super.initState();
-    _selectedPreset = FrequencyInterval.presets[3]; // Default: weekly
+    _activeShortcut = _ShortcutFrequency.weekly;
+    _customIntervalController.text = '1';
+    _customUnit = _CustomUnit.weeks;
     _dueDate = _dateOnly(DateTime.now());
     if (widget.isEditing) {
       _loadExistingTask();
@@ -65,38 +66,45 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
       _effortLevel = task.effortLevel;
       _dueDate = task.nextDueDate;
 
-      // Find matching preset
+      // Populate picker from stored interval
-      _selectedPreset = null;
+      switch (task.intervalType) {
-      _isCustomFrequency = true;
+        case IntervalType.daily:
-      for (final preset in FrequencyInterval.presets) {
+          _customUnit = _CustomUnit.days;
-        if (preset.intervalType == task.intervalType &&
+          _customIntervalController.text = '1';
-            preset.days == task.intervalDays) {
+        case IntervalType.everyNDays:
-          _selectedPreset = preset;
+          // Check if it's a clean week multiple
-          _isCustomFrequency = false;
+          if (task.intervalDays % 7 == 0) {
-          break;
-        }
-      }
-
-      if (_isCustomFrequency) {
-        // Determine custom unit from stored interval
-        switch (task.intervalType) {
-          case IntervalType.everyNMonths:
-            _customUnit = _CustomUnit.months;
-            _customIntervalController.text = task.intervalDays.toString();
-          case IntervalType.monthly:
-            _customUnit = _CustomUnit.months;
-            _customIntervalController.text = '1';
-          case IntervalType.weekly:
             _customUnit = _CustomUnit.weeks;
-            _customIntervalController.text = '1';
+            _customIntervalController.text = (task.intervalDays ~/ 7).toString();
-          case IntervalType.biweekly:
+          } else {
-            _customUnit = _CustomUnit.weeks;
-            _customIntervalController.text = '2';
-          default:
             _customUnit = _CustomUnit.days;
             _customIntervalController.text = task.intervalDays.toString();
-        }
+          }
+        case IntervalType.weekly:
+          _customUnit = _CustomUnit.weeks;
+          _customIntervalController.text = '1';
+        case IntervalType.biweekly:
+          _customUnit = _CustomUnit.weeks;
+          _customIntervalController.text = '2';
+        case IntervalType.monthly:
+          _customUnit = _CustomUnit.months;
+          _customIntervalController.text = '1';
+        case IntervalType.everyNMonths:
+          _customUnit = _CustomUnit.months;
+          _customIntervalController.text = task.intervalDays.toString();
+        case IntervalType.quarterly:
+          _customUnit = _CustomUnit.months;
+          _customIntervalController.text = '3';
+        case IntervalType.yearly:
+          _customUnit = _CustomUnit.months;
+          _customIntervalController.text = '12';
       }
+
+      // Detect matching shortcut chip
+      _activeShortcut = _ShortcutFrequency.fromPickerValues(
+        int.tryParse(_customIntervalController.text) ?? 1,
+        _customUnit,
+      );
     });
   }
 
@@ -224,59 +232,52 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
   }
 
   Widget _buildFrequencySelector(AppLocalizations l10n, ThemeData theme) {
-    final items = <Widget>[];
-
-    // Preset intervals
-    for (final preset in FrequencyInterval.presets) {
-      items.add(
-        ChoiceChip(
-          label: Text(preset.label()),
-          selected: !_isCustomFrequency && _selectedPreset == preset,
-          onSelected: (selected) {
-            if (selected) {
-              setState(() {
-                _selectedPreset = preset;
-                _isCustomFrequency = false;
-              });
-            }
-          },
-        ),
-      );
-    }
-
-    // Custom option
-    items.add(
-      ChoiceChip(
-        label: Text(l10n.taskFormFrequencyCustom),
-        selected: _isCustomFrequency,
-        onSelected: (selected) {
-          if (selected) {
-            setState(() {
-              _isCustomFrequency = true;
-              _selectedPreset = null;
-            });
-          }
-        },
-      ),
-    );
-
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
+        // Shortcut chips row (always visible)
         Wrap(
           spacing: 8,
           runSpacing: 4,
-          children: items,
+          children: [
+            for (final shortcut in _ShortcutFrequency.values)
+              ChoiceChip(
+                label: Text(_shortcutLabel(shortcut, l10n)),
+                selected: _activeShortcut == shortcut,
+                onSelected: (selected) {
+                  if (selected) {
+                    final values = shortcut.toPickerValues();
+                    setState(() {
+                      _activeShortcut = shortcut;
+                      _customIntervalController.text = values.number.toString();
+                      _customUnit = values.unit;
+                    });
+                  }
+                },
+              ),
+          ],
         ),
-        if (_isCustomFrequency) ...[
+        const SizedBox(height: 12),
-          const SizedBox(height: 12),
+        // Freeform picker row (ALWAYS visible — not conditional)
-          _buildCustomFrequencyInput(l10n, theme),
+        _buildFrequencyPickerRow(l10n, theme),
-        ],
       ],
     );
   }
 
-  Widget _buildCustomFrequencyInput(AppLocalizations l10n, ThemeData theme) {
+  String _shortcutLabel(_ShortcutFrequency shortcut, AppLocalizations l10n) {
+    switch (shortcut) {
+      case _ShortcutFrequency.daily:
+        return l10n.frequencyShortcutDaily;
+      case _ShortcutFrequency.weekly:
+        return l10n.frequencyShortcutWeekly;
+      case _ShortcutFrequency.biweekly:
+        return l10n.frequencyShortcutBiweekly;
+      case _ShortcutFrequency.monthly:
+        return l10n.frequencyShortcutMonthly;
+    }
+  }
+
+  Widget _buildFrequencyPickerRow(AppLocalizations l10n, ThemeData theme) {
     return Row(
       children: [
         Text(
@@ -294,6 +295,14 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
             decoration: const InputDecoration(
               contentPadding: EdgeInsets.symmetric(horizontal: 8, vertical: 8),
             ),
+            onChanged: (value) {
+              setState(() {
+                _activeShortcut = _ShortcutFrequency.fromPickerValues(
+                  int.tryParse(value) ?? 1,
+                  _customUnit,
+                );
+              });
+            },
           ),
         ),
         const SizedBox(width: 8),
@@ -315,8 +324,13 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
             ],
             selected: {_customUnit},
             onSelectionChanged: (newSelection) {
+              final newUnit = newSelection.first;
               setState(() {
-                _customUnit = newSelection.first;
+                _customUnit = newUnit;
+                _activeShortcut = _ShortcutFrequency.fromPickerValues(
+                  int.tryParse(_customIntervalController.text) ?? 1,
+                  newUnit,
+                );
               });
             },
           ),
@@ -374,53 +388,32 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
     }
   }
 
-  /// Resolve the frequency from either selected preset or custom input.
+  /// Resolve the frequency from the freeform picker (single source of truth).
+  /// The picker is always the source of truth; shortcut chips just populate it.
   ({IntervalType type, int days, int? anchorDay}) _resolveFrequency() {
-    if (!_isCustomFrequency && _selectedPreset != null) {
-      final preset = _selectedPreset!;
-      // For calendar-anchored intervals, set anchorDay to due date's day
-      int? anchorDay;
-      if (_isCalendarAnchored(preset.intervalType)) {
-        anchorDay = _dueDate.day;
-      }
-      return (
-        type: preset.intervalType,
-        days: preset.days,
-        anchorDay: anchorDay,
-      );
-    }
-
-    // Custom frequency
     final number = int.tryParse(_customIntervalController.text) ?? 1;
     switch (_customUnit) {
       case _CustomUnit.days:
-        return (
+        if (number == 1) {
-          type: IntervalType.everyNDays,
+          return (type: IntervalType.daily, days: 1, anchorDay: null);
-          days: number,
+        }
-          anchorDay: null,
+        return (type: IntervalType.everyNDays, days: number, anchorDay: null);
-        );
       case _CustomUnit.weeks:
-        return (
+        if (number == 1) {
-          type: IntervalType.everyNDays,
+          return (type: IntervalType.weekly, days: 1, anchorDay: null);
-          days: number * 7,
+        }
-          anchorDay: null,
+        if (number == 2) {
-        );
+          return (type: IntervalType.biweekly, days: 14, anchorDay: null);
+        }
+        return (type: IntervalType.everyNDays, days: number * 7, anchorDay: null);
       case _CustomUnit.months:
-        return (
+        if (number == 1) {
-          type: IntervalType.everyNMonths,
+          return (type: IntervalType.monthly, days: 1, anchorDay: _dueDate.day);
-          days: number,
+        }
-          anchorDay: _dueDate.day,
+        return (type: IntervalType.everyNMonths, days: number, anchorDay: _dueDate.day);
-        );
     }
   }
 
-  bool _isCalendarAnchored(IntervalType type) {
-    return type == IntervalType.monthly ||
-        type == IntervalType.everyNMonths ||
-        type == IntervalType.quarterly ||
-        type == IntervalType.yearly;
-  }
-
   Future<void> _onSave() async {
     if (!_formKey.currentState!.validate()) return;
 
@@ -507,5 +500,36 @@ class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
   }
 }
 
-/// Unit options for custom frequency input.
+/// Shortcut frequency options for quick selection chips.
+enum _ShortcutFrequency {
+  daily,
+  weekly,
+  biweekly,
+  monthly;
+
+  /// Returns the picker values (number + unit) that this shortcut represents.
+  ({int number, _CustomUnit unit}) toPickerValues() {
+    switch (this) {
+      case _ShortcutFrequency.daily:
+        return (number: 1, unit: _CustomUnit.days);
+      case _ShortcutFrequency.weekly:
+        return (number: 1, unit: _CustomUnit.weeks);
+      case _ShortcutFrequency.biweekly:
+        return (number: 2, unit: _CustomUnit.weeks);
+      case _ShortcutFrequency.monthly:
+        return (number: 1, unit: _CustomUnit.months);
+    }
+  }
+
+  /// Returns the matching shortcut for given picker values, or null if no match.
+  static _ShortcutFrequency? fromPickerValues(int number, _CustomUnit unit) {
+    if (number == 1 && unit == _CustomUnit.days) return _ShortcutFrequency.daily;
+    if (number == 1 && unit == _CustomUnit.weeks) return _ShortcutFrequency.weekly;
+    if (number == 2 && unit == _CustomUnit.weeks) return _ShortcutFrequency.biweekly;
+    if (number == 1 && unit == _CustomUnit.months) return _ShortcutFrequency.monthly;
+    return null;
+  }
+}
+
+/// Unit options for freeform frequency picker.
 enum _CustomUnit { days, weeks, months }

lib/l10n/app_de.arb

@@ -48,6 +48,10 @@
   "taskFormFrequencyLabel": "Wiederholung",
   "taskFormFrequencyCustom": "Benutzerdefiniert",
   "taskFormFrequencyEvery": "Alle",
+  "frequencyShortcutDaily": "Täglich",
+  "frequencyShortcutWeekly": "Wöchentlich",
+  "frequencyShortcutBiweekly": "Alle 2 Wochen",
+  "frequencyShortcutMonthly": "Monatlich",
   "taskFormFrequencyUnitDays": "Tage",
   "taskFormFrequencyUnitWeeks": "Wochen",
   "taskFormFrequencyUnitMonths": "Monate",

lib/l10n/app_localizations.dart

@@ -322,6 +322,30 @@ abstract class AppLocalizations {
   /// **'Alle'**
   String get taskFormFrequencyEvery;
 
+  /// No description provided for @frequencyShortcutDaily.
+  ///
+  /// In de, this message translates to:
+  /// **'Täglich'**
+  String get frequencyShortcutDaily;
+
+  /// No description provided for @frequencyShortcutWeekly.
+  ///
+  /// In de, this message translates to:
+  /// **'Wöchentlich'**
+  String get frequencyShortcutWeekly;
+
+  /// No description provided for @frequencyShortcutBiweekly.
+  ///
+  /// In de, this message translates to:
+  /// **'Alle 2 Wochen'**
+  String get frequencyShortcutBiweekly;
+
+  /// No description provided for @frequencyShortcutMonthly.
+  ///
+  /// In de, this message translates to:
+  /// **'Monatlich'**
+  String get frequencyShortcutMonthly;
+
   /// No description provided for @taskFormFrequencyUnitDays.
   ///
   /// In de, this message translates to:

lib/l10n/app_localizations_de.dart

@@ -128,6 +128,18 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get taskFormFrequencyEvery => 'Alle';
 
+  @override
+  String get frequencyShortcutDaily => 'Täglich';
+
+  @override
+  String get frequencyShortcutWeekly => 'Wöchentlich';
+
+  @override
+  String get frequencyShortcutBiweekly => 'Alle 2 Wochen';
+
+  @override
+  String get frequencyShortcutMonthly => 'Monatlich';
+
   @override
   String get taskFormFrequencyUnitDays => 'Tage';