Add OpenAPI specification and Swagger UI for REST API documentation

[treblereel]

Context

Part of epic #1 — Build production-ready REST microservice with k8s deployment on top of casehub-engine. API consumers need auto-generated documentation to understand endpoints, request/response schemas, and integration patterns.

What

Configure OpenAPI spec generation and Swagger UI:

• /q/openapi — OpenAPI 3.0 spec (JSON/YAML)
• /q/swagger-ui — interactive Swagger UI for testing endpoints
• Annotate all REST endpoints with proper OpenAPI metadata

Acceptance Criteria

• OpenAPI spec available at /q/openapi in both JSON and YAML formats
• Swagger UI accessible at /q/swagger-ui with all API v1 endpoints
• All endpoints documented with @operation, @apiresponse, @parameter annotations
• Request/response schemas include descriptions and examples
• Error responses (400, 404, 409, 500) documented with RFC 7807 problem details schema
• API info section includes title, version, description, contact
• Integration tests verify OpenAPI spec is valid and includes all endpoints

Notes

• Use quarkus-smallrye-openapi extension
• Enable Swagger UI in dev mode, optionally disable in production via config
• Add OpenAPI annotations to all JAX-RS resources created in issues Implement REST API v1 — case definition discovery endpoints #2, Implement REST API v1 — case lifecycle endpoints (start, status, context queries) #4, Implement REST API v1 — signal endpoint for external events #5, Implement REST API v1 — case control operations (suspend, resume, cancel) #6, Implement REST API v1 — event log/audit trail endpoint #7
• Consider adding request/response examples using @Schema(example = "...")
• File paths: REST resource classes, OpenAPI configuration in application.properties