Stub backend endpoints

[bostdiek]

Description:
Create FastAPI routes with v1 versioning and comprehensive endpoint stubs.

Developer Story:
As a developer, I want versioned API endpoints so the frontend can reliably integrate while maintaining future flexibility.

Acceptance Criteria:
• API routes structured under /api/v1/:

• GET /api/v1/health (health check)
• GET /api/v1/recipes (list recipes with pagination)
• POST /api/v1/recipes (create recipe)
• GET /api/v1/recipes/{id} (get recipe with ingredients)
• PUT /api/v1/recipes/{id} (update recipe)
• DELETE /api/v1/recipes/{id} (delete recipe)
• GET /api/v1/ingredients (list ingredients)
• POST /api/v1/ingredients (create ingredient)
  • All endpoints return mock data with proper HTTP status codes
  • OpenAPI docs available at /api/v1/docs
  • Response schemas match shared type definitions
  • CORS configured for both dev (localhost:5173) and prod origins
  • Request/response validation using Pydantic schemas