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>

docker-compose.yml

@@ -0,0 +1,24 @@
+services:
+  couch-potato:
+    build: .
+    image: couch-potato
+    container_name: couch-potato
+    restart: unless-stopped
+    ports:
+      - "3000:3000"
+    volumes:
+      - couch-potato-data:/data
+    environment:
+      - DATABASE_URL=file:/data/sqlite.db
+      - TMDB_API_KEY=${TMDB_API_KEY}
+      - BETTER_AUTH_SECRET=${BETTER_AUTH_SECRET}
+      - BETTER_AUTH_URL=${BETTER_AUTH_URL:-http://localhost:3000}
+    healthcheck:
+      test: ["CMD", "node", "-e", "fetch('http://localhost:3000/api/health').then(r=>{if(!r.ok)process.exit(1)}).catch(()=>process.exit(1))"]
+      interval: 30s
+      timeout: 10s
+      start_period: 30s
+      retries: 3
+
+volumes:
+  couch-potato-data: