Add dedicated Drizzle config files for sqlite and postgres and generate
new migration outputs for each dialect.
Update migrate scripts to load env files and auto-pick the correct
config unless explicitly provided, and tighten API auth handling by
using shared auth context helpers and enforcing userId checks when auth
is enabled.
- replace custom DB adapter with Drizzle setup (SQLite/Postgres schemas) and add `drizzle.config.ts` plus migrations in `drizzle/` and `drizzle_pg/`
- switch better-auth to drizzleAdapter, add auth helpers (`getAuthContext`, `requireAuthContext`, `requireAudiobookOwned`), and make `useAuth`/`useAuthSession` safe no-ops when auth is disabled
- persist documents/audiobooks in DB with ownership checks, unclaimed fallback, and ref-counted deletes; add FS scan helper for no-auth mode
- gate docx-to-pdf, library, voices, whisper, and migration endpoints behind auth when enabled
- add unclaimed data scan/claim flow with `/api/user/claim`, `ClaimDataModal`, and server-side scan/claim helpers
- refactor rate limiting and account deletion to use Drizzle tables (`user_tts_chars`, `user`)
- run migrations via `scripts/migrate-if-auth.mjs` (auto on `pnpm start` + `pnpm migrate`), remove Docker entrypoint and old better-auth migration file
- update README and lockfile for the new migration workflow and dependencies
