refactor: use environment-specific .env files

- Rename .env.example to .env.development.example
- Update docker-compose.yml to use env_file for dev backend
- Update .gitignore to ignore .env.development and .env.production
- Remove generic .env and .env.example in favor of:
  * .env.development (dev) + .env.development.example (template)
  * .env.production (prod) + .env.production.example (template)

backend/.env.development.example

@@ -0,0 +1,24 @@
+# Server
+NODE_ENV=development
+PORT=3000
+
+# CORS
+CORS_ORIGIN=http://localhost:8080
+
+# Database
+DATABASE_URL=postgresql://spotlightcam:spotlightcam123@db:5432/spotlightcam
+
+# JWT
+JWT_SECRET=dev-secret-key-12345-change-in-production
+JWT_EXPIRES_IN=24h
+
+# AWS SES (REPLACE WITH YOUR CREDENTIALS)
+AWS_REGION=eu-central-1
+AWS_ACCESS_KEY_ID=your-aws-access-key-id
+AWS_SECRET_ACCESS_KEY=your-aws-secret-access-key
+SES_FROM_EMAIL=noreply@spotlight.cam
+SES_FROM_NAME=spotlight.cam
+
+# Email Settings
+FRONTEND_URL=http://localhost:8080
+VERIFICATION_TOKEN_EXPIRY=24h