T-5: set up API-first tooling with OpenAPI spec as single source of truth

Backend: openapi-generator-maven-plugin generates Spring interfaces and DTOs
from the spec. Frontend: openapi-typescript + openapi-fetch provide type-safe
API access. Both sides get compile-time contract enforcement from a single
api.yaml file.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/package.json

@@ -4,8 +4,9 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "dev": "vite",
-    "build": "run-p type-check \"build-only {@}\" --",
+    "generate:api": "openapi-typescript ../backend/src/main/resources/openapi/api.yaml -o src/api/schema.d.ts",
+    "dev": "npm run generate:api && vite",
+    "build": "npm run generate:api && run-p type-check \"build-only {@}\" --",
     "preview": "vite preview",
     "test:unit": "vitest",
     "build-only": "vite build",
@@ -16,6 +17,7 @@
     "format": "prettier --write --experimental-cli src/"
   },
   "dependencies": {
+    "openapi-fetch": "^0.17.0",
     "vue": "^3.5.29",
     "vue-router": "^5.0.3"
   },
@@ -35,6 +37,7 @@
     "jiti": "^2.6.1",
     "jsdom": "^28.1.0",
     "npm-run-all2": "^8.0.4",
+    "openapi-typescript": "^7.13.0",
     "oxlint": "~1.50.0",
     "prettier": "3.8.1",
     "typescript": "~5.9.3",