feat(settings): add compact database card to General section

Adds get_database_info and vacuum_database Tauri commands. The General
section now shows current DB size and reclaimable space on load, with a
Compact now button that runs PRAGMA wal_checkpoint(FULL) + VACUUM and
reports how many MB were freed. Button disables automatically when the
database is already compact (< 0.5 MB reclaimable).

src-tauri/src/lib.rs

@@ -144,6 +144,8 @@ pub fn run() {
             commands::get_tagging_queue_folder_ids,
             commands::set_tagging_queue_folder_ids,
             commands::open_app_data_folder,
+            commands::get_database_info,
+            commands::vacuum_database,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");