feat(11-02): render pre-populated tasks with muted visual distinction in calendar UI

- Add isPrePopulated parameter to CalendarTaskRow (default false, backward compat)
- Wrap ListTile in Opacity(0.55) when isPrePopulated to indicate upcoming tasks
- Render 'Demnächst' section in CalendarDayList with muted section header
- Update _buildAnimatedTaskRow to accept and forward isPrePopulated flag
- Update _CompletingTaskRow to accept isPrePopulated (always false during animation)
- Update celebration check to include prePopulatedTasks.isEmpty condition
- Update _completingTaskIds cleanup to also check prePopulatedTasks

lib/features/home/presentation/calendar_day_list.dart

@@ -58,7 +58,8 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
         // Clean up animation IDs for tasks that are no longer in the data.
         _completingTaskIds.removeWhere((id) =>
             !state.overdueTasks.any((t) => t.task.id == id) &&
-            !state.dayTasks.any((t) => t.task.id == id));
+            !state.dayTasks.any((t) => t.task.id == id) &&
+            !state.prePopulatedTasks.any((t) => t.task.id == id));
 
         return _buildContent(context, state, l10n, theme);
       },
@@ -82,8 +83,12 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
 
     // State (e): Celebration — today is selected and all tasks are done
     // (totalTaskCount > 0 so at least some task exists somewhere, but today
-    // has none remaining after completion).
-    if (isToday && state.dayTasks.isEmpty && state.overdueTasks.isEmpty && state.totalTaskCount > 0) {
+    // has none remaining after completion, including no pre-populated tasks).
+    if (isToday &&
+        state.dayTasks.isEmpty &&
+        state.overdueTasks.isEmpty &&
+        state.prePopulatedTasks.isEmpty &&
+        state.totalTaskCount > 0) {
       return _buildCelebration(l10n, theme);
     }
 
@@ -269,6 +274,24 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
       ));
     }
 
+    // Pre-populated tasks section (upcoming tasks within interval window).
+    if (state.prePopulatedTasks.isNotEmpty) {
+      items.add(_buildSectionHeader(
+        'Demnächst',
+        theme,
+        color: theme.colorScheme.onSurface.withValues(alpha: 0.5),
+      ));
+      for (final tw in state.prePopulatedTasks) {
+        items.add(_buildAnimatedTaskRow(
+          tw,
+          isOverdue: false,
+          showRoomTag: showRoomTag,
+          canComplete: true,
+          isPrePopulated: true,
+        ));
+      }
+    }
+
     return ListView(children: items);
   }
 
@@ -291,6 +314,7 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
     required bool isOverdue,
     required bool showRoomTag,
     required bool canComplete,
+    bool isPrePopulated = false,
   }) {
     final isCompleting = _completingTaskIds.contains(tw.task.id);
 
@@ -300,6 +324,7 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
         taskWithRoom: tw,
         isOverdue: isOverdue,
         showRoomTag: showRoomTag,
+        isPrePopulated: false, // Completing tasks always show full styling.
       );
     }
 
@@ -309,6 +334,7 @@ class _CalendarDayListState extends ConsumerState<CalendarDayList> {
       isOverdue: isOverdue,
       showRoomTag: showRoomTag,
       canComplete: canComplete,
+      isPrePopulated: isPrePopulated,
       onCompleted: () => _onTaskCompleted(tw.task.id),
     );
   }
@@ -321,11 +347,13 @@ class _CompletingTaskRow extends StatefulWidget {
     required this.taskWithRoom,
     required this.isOverdue,
     required this.showRoomTag,
+    this.isPrePopulated = false,
   });
 
   final TaskWithRoom taskWithRoom;
   final bool isOverdue;
   final bool showRoomTag;
+  final bool isPrePopulated;
 
   @override
   State<_CompletingTaskRow> createState() => _CompletingTaskRowState();
@@ -372,6 +400,7 @@ class _CompletingTaskRowState extends State<_CompletingTaskRow>
           taskWithRoom: widget.taskWithRoom,
           isOverdue: widget.isOverdue,
           showRoomTag: widget.showRoomTag,
+          isPrePopulated: widget.isPrePopulated,
           onCompleted: () {}, // Already completing — ignore repeat taps.
         ),
       ),

lib/features/home/presentation/calendar_task_row.dart

@@ -14,6 +14,10 @@ const _overdueColor = Color(0xFFE07A5F);
 ///
 /// When [isOverdue] is true the task name uses coral text to visually
 /// distinguish overdue carry-over from today's regular tasks.
+///
+/// When [isPrePopulated] is true the entire row is rendered at 0.55 opacity
+/// to indicate it is not yet due (visible within interval window, but due
+/// date is in the future).
 class CalendarTaskRow extends StatelessWidget {
   const CalendarTaskRow({
     super.key,
@@ -22,6 +26,7 @@ class CalendarTaskRow extends StatelessWidget {
     this.isOverdue = false,
     this.showRoomTag = true,
     this.canComplete = true,
+    this.isPrePopulated = false,
   });
 
   final TaskWithRoom taskWithRoom;
@@ -38,12 +43,16 @@ class CalendarTaskRow extends StatelessWidget {
   /// When false, the checkbox is disabled (e.g. for future tasks).
   final bool canComplete;
 
+  /// When true, the row is rendered at 0.55 opacity to indicate an
+  /// upcoming (not-yet-due) pre-populated task within its interval window.
+  final bool isPrePopulated;
+
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
     final task = taskWithRoom.task;
 
-    return ListTile(
+    final tile = ListTile(
       onTap: () => context.go(
         '/rooms/${taskWithRoom.roomId}/tasks/${taskWithRoom.task.id}',
       ),
@@ -79,5 +88,7 @@ class CalendarTaskRow extends StatelessWidget {
             )
           : null,
     );
+
+    return isPrePopulated ? Opacity(opacity: 0.55, child: tile) : tile;
   }
 }