v0.1.0 - Order Service MVP

Initial milestone release of OrderFlow Order Service.

Features:

• Layered architecture (Controller / Service / Repository)
• PostgreSQL persistence via Spring Data JPA
• DTO separation with validation
• Pagination support
• Structured global exception handling
• OpenAPI (Swagger UI) documentation
• API versioning under /api/v1
• Actuator endpoints enabled

This version represents the first production-oriented baseline of the service.