fix(v1.5.0): Silent-Sync Mode + UI Improvements

Silent-Sync Implementation (Auto-Sync Banner Fix):
- Add SYNCING_SILENT state to SyncStateManager for background syncs
- Auto-sync (onResume) now triggers silently without banner interruption
- Silent-sync state blocks additional manual syncs (mutual exclusion)
- Error banners still display even after silent-sync failures
- SyncStatus tracks 'silent' flag to hide COMPLETED banners after silent-sync

UI/UX Improvements (from v1.5.0 post-migration fixes):
- Fix text wrapping in checklist items (singleLine=false, maxLines=5)
- Fix cursor position in text notes (use TextFieldValue with TextRange)
- Display app icon instead of emoji in AboutScreen
- Add smooth slide animations for NoteEditor transitions
- Remove visual noise from AboutScreen icon

Technical Changes:
- ComposeNoteEditorActivity: Add back animation with OnBackPressedCallback
- ComposeMainActivity: Add entry/exit slide animations for note editing
- NoteEditorScreen: Use TextFieldValue for proper cursor positioning
- ChecklistItemRow: Enable text wrapping for long checklist items
- AboutScreen: Convert Drawable to Bitmap via Canvas (supports AdaptiveIcon)
- SyncStatusBanner: Exclude SYNCING_SILENT from visibility checks
- MainActivity: Update legacy auto-sync to use silent mode

Fixes #[auto-sync-banner], improves #[user-experience]

Branch: feature/v1.5.0

android/app/src/main/java/dev/dettmer/simplenotes/MainActivity.kt

@@ -182,6 +182,11 @@ class MainActivity : AppCompatActivity() {
                     swipeRefreshLayout.isRefreshing = false
                     syncStatusBanner.visibility = View.GONE
                 }
+                // v1.5.0: Silent-Sync - Banner nicht anzeigen, aber Sync-Controls deaktivieren
+                SyncStateManager.SyncState.SYNCING_SILENT -> {
+                    setSyncControlsEnabled(false)
+                    // Kein Banner anzeigen bei Silent-Sync (z.B. onResume Auto-Sync)
+                }
             }
         }
     }
@@ -222,6 +227,7 @@ class MainActivity : AppCompatActivity() {
      * - Nur Success-Toast (kein "Auto-Sync..." Toast)
      * 
      * NOTE: WiFi-Connect Sync nutzt WorkManager (auch wenn App geschlossen!)
+     * v1.5.0: Silent-Sync - kein Banner während des Syncs, Fehler werden trotzdem angezeigt
      */
     private fun triggerAutoSync(source: String = "unknown") {
         // Throttling: Max 1 Sync pro Minute
@@ -230,7 +236,8 @@ class MainActivity : AppCompatActivity() {
         }
         
         // 🔄 v1.3.1: Check if sync already running
-        if (!SyncStateManager.tryStartSync("auto-$source")) {
+        // v1.5.0: silent=true - kein Banner bei Auto-Sync
+        if (!SyncStateManager.tryStartSync("auto-$source", silent = true)) {
             Logger.d(TAG, "⏭️ Auto-sync ($source): Another sync already in progress")
             return
         }