Expanded folder sync functionality to support multiple folders and improved performance. (#47)

- Added `SyncedFolder` data class and transitioned from a single `syncedFolderUri` to a list of `syncedFolders`.
- Implemented logic to add, remove, and persist multiple synced folders using JSON in shared preferences, including a migration path for legacy single-folder settings.
- Updated `FolderSyncWorker` to iterate through all registered folders and added an annotation sidecar preloading optimization to reduce file I/O during sync.
- Redesigned the "Folder Sync" UI in `LibraryScreen` to display a list of active folders with individual management options and a 3-folder limit.
- Refined permission handling to request both read and write access for synced folders.

app/src/main/java/com/aryan/reader/HomeScreen.kt

@@ -345,16 +345,15 @@ fun HomeScreen(
                                     onRefresh = { viewModel.refreshLibrary() },
                                     isRefreshing = uiState.isRefreshing,
                                     isSyncEnabled = uiState.isSyncEnabled,
-                                    hasSyncedFolder = uiState.syncedFolderUri != null
+                                    hasSyncedFolder = uiState.syncedFolders.isNotEmpty()
                                 )
                             }
                         }
 
-                        // Loading Indicator Overlay
                         if (uiState.isLoading) {
                             Surface(
                                 modifier = Modifier.fillMaxSize(),
-                                color = MaterialTheme.colorScheme.background.copy(alpha = 0.7f) // Semi-transparent overlay
+                                color = MaterialTheme.colorScheme.background.copy(alpha = 0.7f)
                             ) {
                                 Box(
                                     modifier = Modifier.fillMaxSize(),