Contract-first API with DTOs, validation, and server-side OpenAPI post-processing

Add dedicated request/response DTOs for all controllers, replacing raw
JsonNode parameters with validated types. Move OpenAPI path-prefix stripping
and ProcessorNode children injection into OpenApiCustomizer beans so the
spec served at /api/v1/api-docs is already clean — eliminating the need for
the ui/scripts/process-openapi.mjs post-processing script.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/package.json

@@ -8,7 +8,8 @@
     "build": "tsc -b && vite build",
     "lint": "eslint .",
     "preview": "vite preview",
-    "generate-api": "openapi-typescript http://localhost:8081/api/v1/api-docs -o src/api/schema.d.ts"
+    "generate-api": "openapi-typescript src/api/openapi.json -o src/api/schema.d.ts",
+    "generate-api:live": "curl -s http://localhost:8081/api/v1/api-docs -o src/api/openapi.json && openapi-typescript src/api/openapi.json -o src/api/schema.d.ts"
   },
   "dependencies": {
     "@tanstack/react-query": "^5.90.21",