Add Docker packaging and migrate from better-sqlite3 to libsql

Docker self-hosting support:
- Dockerfile (multi-stage Alpine build with tini init)
- docker-compose.yml with named volume for SQLite persistence
- /api/health endpoint for container health checks
- Auto-migration on startup via drizzle-orm/libsql/migrator
- Graceful shutdown (SIGTERM stops scheduler, closes DB)
- Next.js standalone output mode for minimal image size

Database driver migration (better-sqlite3 → @libsql/client):
- Eliminates native C++ compilation, enabling Alpine Docker images
- All DB queries converted from sync to async across services and routes
- DATABASE_URL now uses libsql file: prefix format
- drizzle.config.ts dialect changed to turso for libsql support
- Initial migration files generated in drizzle/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -1,4 +1,11 @@
-DATABASE_URL=sqlite.db
+# SQLite database URL (Docker: file:/data/sqlite.db, local dev: file:sqlite.db)
+DATABASE_URL=file:sqlite.db
+
+# TMDB API key — get one at https://www.themoviedb.org/settings/api
 TMDB_API_KEY=your_tmdb_api_key_here
+
+# Random secret for session encryption (min 32 chars)
 BETTER_AUTH_SECRET=your_secret_here
+
+# Public URL of your instance
 BETTER_AUTH_URL=http://localhost:3000