feat(v1.5.0): Complete NoteEditor Redesign with Jetpack Compose

Features:
- Migrate NoteEditorActivity from XML to Jetpack Compose
- Support both TEXT and CHECKLIST note types
- FOSS native drag & drop using Compose Foundation APIs (no external dependencies)
- Auto-keyboard focus with explicit keyboard controller show() calls
- Consistent placeholder text for empty checklist items
- Unified delete dialog with Server/Local deletion options

Components:
- ComposeNoteEditorActivity: Activity wrapper with ViewModelFactory for SavedStateHandle
- NoteEditorScreen: Main editor screen supporting TEXT and CHECKLIST modes
- NoteEditorViewModel: State management with WebDav server deletion support
- ChecklistItemRow: Individual checklist item with drag handle, checkbox, text input
- DragDropState: FOSS drag & drop implementation using LazyListState

Improvements:
- Auto-keyboard shows when creating new notes (focuses title/content)
- Keyboard consistently shows when adding new checklist items
- Placeholder text 'Neues Element…' for empty list items
- Delete dialog unified with MainScreen (Server/Local options)
- Server deletion via WebDavSyncService.deleteNoteFromServer()

Debug Enhancements:
- Debug builds have orange icon background (#FFB74D) with red badge
- Debug builds show 'Simple Notes (Debug)' app name
- Easy differentiation between debug and release APKs in launcher

Build Status:
- compileStandardDebug: SUCCESS
- No breaking changes to existing XML-based screens
- Material 3 theming with Dynamic Colors (Material You) applied

Migration Notes:
- Old NoteEditorActivity (XML-based) remains for reference/backwards compatibility
- All editor UI is now Compose-based
- ComposeMainActivity updated to use new ComposeNoteEditorActivity
- Plan document (v1.5.0_EXTENDED_FEATURES_PLAN.md) updated with implementation details

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

@@ -19,6 +19,7 @@
     <string name="content">Inhalt</string>
     <string name="save">Speichern</string>
     <string name="delete">Löschen</string>
+    <string name="back">Zurück</string>
     
     <!-- Note List Item (Preview placeholders) -->
     <string name="note_title_placeholder">Note Title</string>
@@ -81,6 +82,7 @@
     <string name="add_item">Element hinzufügen</string>
     <string name="item_placeholder">Neues Element…</string>
     <string name="reorder_item">Element verschieben</string>
+    <string name="drag_to_reorder">Ziehen zum Sortieren</string>
     <string name="delete_item">Element löschen</string>
     <string name="note_is_empty">Notiz ist leer</string>
     <string name="note_saved">Notiz gespeichert</string>