fix: bundle migration script and ensure file_hash column exists

- Compile src/db/migrate.ts to dist/migrate.js during build
- Copy dist/migrate.js to Stage 2 (runner) inside Dockerfile
- Run bun dist/migrate.js on db:migrate command
- Modify schema.sql to use CREATE TABLE IF NOT EXISTS and ALTER TABLE to add file_hash to existing database instances on VPS

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Dockerfile

@@ -22,6 +22,7 @@ WORKDIR /usr/src/app
 
 # Copy built files, schema, and package.json
 COPY --from=builder /usr/src/app/dist/index.js ./dist/index.js
+COPY --from=builder /usr/src/app/dist/migrate.js ./dist/migrate.js
 COPY schema.sql ./
 COPY package.json ./