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.

src-tauri/src/domains/tombstone/commands.rs

@@ -40,7 +40,6 @@ fn get_session(session: &State<SessionState>) -> Result<(String, Lang), AppError
 }
 
 #[derive(Serialize)]
-#[serde(rename_all = "camelCase")]
 pub struct TombstoneRecord {
     pub table_name: String,
     pub entity_id: String,
@@ -63,7 +62,6 @@ pub fn get_tombstones_since(since: i64, db: State<DbManager>, session: State<Ses
 }
 
 #[derive(Deserialize)]
-#[serde(rename_all = "camelCase")]
 pub struct TombstoneInput {
     pub table_name: String,
     pub entity_id: String,