Add a dev-only Vite UI mode with Tauri API mocks, in-memory fixture scenarios, reusable media source handling, and documentation for browser-based visual testing.
Sets up Tauri v2 + React frontend with SQLite metadata store,
sqlite-vec for CLIP embedding infrastructure, and r2d2 connection
pool replacing the single Arc<Mutex<Connection>>. Indexer now uses
rayon for parallel file metadata collection.