phase 16: vitest + MSW frontend tests, CI integration

frontend/package.json

@@ -7,7 +7,9 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest --run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "@monaco-editor/react": "^4.7.0",
@@ -22,6 +24,9 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^24.12.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
@@ -30,8 +35,11 @@
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.5.2",
     "globals": "^17.4.0",
+    "jsdom": "^29.0.2",
+    "msw": "^2.13.2",
     "typescript": "~6.0.2",
     "typescript-eslint": "^8.58.0",
-    "vite": "^8.0.4"
+    "vite": "^8.0.4",
+    "vitest": "^4.1.4"
   }
 }