Introduce local fallback for book creation and improve error handling

- Added support for creating books locally when the cloud limit is reached.
- Enhanced error handling in `AddNewBookForm` with `ApiError` and fallback logic for local book creation.
- Implemented `BookTypeLimit` to manage type-specific book limits with visual indicators in `BookList`.
- Refactored `TombstoneRecord` to standardize naming conventions for better API compatibility.
- Updated `useSyncSeries` and `useSyncBooks` to handle empty tombstones gracefully.
- Updated locales with new translations for fallback and error messaging.

lib/tauri.ts

@@ -44,10 +44,10 @@ export interface SyncCheckResult {
 }
 
 export interface TombstoneRecord {
-    tableName: string;
-    entityId: string;
-    bookId: string | null;
-    deletedAt: number;
+    table_name: string;
+    entity_id: string;
+    book_id: string | null;
+    deleted_at: number;
 }
 
 // ─── User & Auth ───────────────────────────────────────────