feat(api): implement OpenAPI/REST API for file conversions

- Add comprehensive REST API at /api/v1 with modular structure
- Implement authentication endpoints (register, login, logout, me)
- Add converter listing and format discovery endpoints
- Create job management and file download endpoints
- Add health check endpoint for monitoring
- Set up CORS support for browser-based API clients
- Create API middleware for JWT authentication
- Add environment variables for API configuration
- Include comprehensive API documentation and test script

Infrastructure:
- Enhanced CI/CD workflow for custom Docker registries
- Docker Compose setup with dev, prod, and monitoring profiles
- Claude.ai integration files for development workflow
- Environment-based configuration with .env.development

Known limitations:
- JWT authentication context needs fixing (using ALLOW_UNAUTHENTICATED=true)
- Swagger UI temporarily disabled due to composition error
- File upload endpoint needs multipart/form-data support

The API code is isolated in src/api/ directory to maintain separation
from the existing codebase, making it easy to maintain or contribute back.

.env.development

@@ -0,0 +1,15 @@
+# Development environment variables
+ACCOUNT_REGISTRATION=true
+JWT_SECRET=dev-secret-key-123
+HTTP_ALLOWED=true
+ALLOW_UNAUTHENTICATED=true
+AUTO_DELETE_EVERY_N_HOURS=24
+WEBROOT=
+TZ=UTC
+
+# API Configuration
+API_ENABLED=true
+API_PREFIX=/api/v1
+API_RATE_LIMIT=100
+API_RATE_WINDOW=15m
+API_KEY_ENABLED=false