MongoDB works great for servers but won't run on mobile (Termux/Android, iOS) or embedded environments.

A SQLite backend for the /db/ route would provide the same JSON-LD document storage with:

• No daemon process required
• Single file storage
• Works on mobile via better-sqlite3 or sql.js (pure WASM)

The storage API in src/db/store.js (findOne, upsertOne, deleteOne, listByPrefix) stays the same — just a different backend implementation.

Could auto-detect: use MongoDB if --mongo is set, fall back to SQLite otherwise via --db-sqlite or similar flag.