refactor: complete configuration cleanup and consistency fixes

- Create docker-compose.dev.yml with Mailhog for development email testing
- Standardize all configurations to use PORT=3001 for backend
- Fix database service naming (postgres → db) across all files
- Add missing BACKEND_URL environment variable to all configs
- Update .env examples to match actual Docker setup requirements
- Remove orphaned postgres-init directory (Umami handles its own DB)
- Update README roadmap: mark gallery feedback as implemented, add multi-admin support
- Update deployment guide with development setup instructions
- Fix frontend Dockerfile.dev for proper hot-reload development
- Remove unused files (wedding-photos.db, frontend/README.md)

This ensures all configuration files are consistent and aligned with the deployment guide.

docker-compose.prod.yml

@@ -12,10 +12,11 @@ services:
       - db
     environment:
       - NODE_ENV=production
-      - PORT=3000
+      - PORT=3001
       - JWT_SECRET=${JWT_SECRET}
       - ADMIN_URL=${ADMIN_URL}
       - FRONTEND_URL=${FRONTEND_URL}
+      - BACKEND_URL=${BACKEND_URL}
       # Database
       - DATABASE_CLIENT=pg
       - DB_HOST=db