feat(edit): form redesign, optional fields, OptionCard dialogs, expressive motion

Post-v1.2.0 design iteration on the event form, reviewed slice by slice
on-device:

- Form rebuilt on the detail screen's card system: tonal EditCards with
  gutter icons (centred on the first row, top-aligned for multiline),
  borderless inline fields (placeholders at half opacity), calendar-coloured
  title accent, no dividers, bare top bar
- Optional sections (location, description, reminders, availability,
  visibility) with per-user defaults in Settings ("New event form" toggles);
  hidden ones unfold via a "More fields" picker dialog
- Reminders: stacked rows + full-width borderless add; two-step picker
  (one-tap presets, then custom amount + minutes/hours/days/weeks dropdown);
  written as METHOD_ALERT Reminders rows. Availability busy/free segmented
  toggle; visibility selector with per-level icons
- OptionCard (ui/common) is now the app-wide selection-dialog standard;
  calendar picker, visibility, more-fields, reminder presets and the
  recurring-delete chooser all use it — radio-row dialogs removed
- MaterialExpressiveTheme with MotionScheme.standard() (expressive bounce
  felt overdone); FAB stack + field reveals animate on theme springs;
  jump-to-today slides toward today's actual direction
- IME: adjustResize + imePadding so the keyboard never pans the form
- Tests: form-field prefs round-trips, availability/access provider
  mappings; DE+EN strings throughout

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/res/values/strings.xml

@@ -68,6 +68,20 @@
     <string name="event_edit_error_no_calendar">No writable calendar available</string>
     <string name="event_edit_save_failed">Couldn\'t save the event</string>
     <string name="event_edit_write_denied">Calendula needs write access to create events</string>
+    <string name="event_edit_more_fields">More fields</string>
+    <string name="event_edit_add">Add</string>
+    <string name="event_edit_add_reminder">Add reminder</string>
+    <string name="event_edit_remove_reminder">Remove reminder</string>
+    <string name="event_edit_reminder_custom">Custom</string>
+    <string name="reminder_unit_minutes">minutes</string>
+    <string name="reminder_unit_hours">hours</string>
+    <string name="reminder_unit_days">days</string>
+    <string name="reminder_unit_weeks">weeks</string>
+    <string name="event_edit_availability">Availability</string>
+    <string name="event_edit_visibility">Visibility</string>
+    <string name="event_availability_busy">Busy</string>
+    <string name="event_access_default">Default</string>
+    <string name="event_access_public">Public</string>
     <string name="event_detail_all_day">All day</string>
     <string name="event_detail_calendar">Calendar</string>
     <string name="event_detail_calendar_unknown">Unknown calendar</string>
@@ -150,6 +164,8 @@
     <string name="settings_week_start_auto">Automatic</string>
     <string name="settings_week_start_monday">Monday</string>
     <string name="settings_week_start_sunday">Sunday</string>
+    <string name="settings_section_event_form">New event form</string>
+    <string name="settings_form_fields_hint">Fields shown by default — everything else sits behind \"More fields\"</string>
     <string name="settings_section_language">Language</string>
     <string name="settings_language">App language</string>
     <string name="settings_language_auto">System default</string>