General improvments (#114)

* Add "Keep Screen On" feature to PDF and Epub readers.

* Add `rawLibraryFiles` to `MainViewModel` and improve file path resolution in `SharedComposables`.

Specifically:
- Updated `MainViewModel` state and UI logic to track and provide unfiltered library files.
- Enhanced file path formatting in `SharedComposables` to better handle Document, Tree, and primary storage URIs.
- Added scrollable support for long text values in `DetailItem` composable.
- Passed `rawLibraryFiles` to `FolderSyncScreen` to ensure sync logic uses the base file list.

* Update info bar background and text colors in EpubReaderScreen to match the selected theme.

* Prevent accidental UI bar toggles immediately after scrolling in EPUB vertical mode.

* feat: implement EPUB highlights sync and legacy migration

- Implement Cloud and Local Folder sync for EPUB highlights.
- Add highlight JSON serialization/deserialization helpers in EpubReaderAnnotations.
- Implement automatic migration of highlights from SharedPreferences to the Database on book open.
- Add cleanup logic to remove legacy SharedPreferences data after successful DB migration.
- Update RecentFilesRepository to trigger local folder metadata sync when highlights are modified.
- Update FolderSyncWorker to pull highlights and custom names from linked folder metadata.

* Update intent filters

app/src/oss/java/com/aryan/reader/data/FirestoreRepository.kt

@@ -23,7 +23,8 @@ data class BookMetadata(
     val lastModifiedTimestamp: Long = 0L,
     val bookmarksJson: String? = null,
     val hasAnnotations: Boolean = false,
-    val customName: String? = null
+    val customName: String? = null,
+    val highlightsJson: String? = null
 )
 
 data class DeviceItem(