test: Vitest + RTL component tests with mocked Wails bindings

- vitest + jsdom + @testing-library/react setup
- mocked wailsjs/go/main/MatrixService + runtime
- tests for: LoginScreen, App routing, HomeScreen auto-relogin,
  RoomList, Composer, EventBubble
- pnpm test runs the suite

Frontend coverage for matrix_client_pc (flow 0010 PC client).

frontend/package.json

@@ -6,7 +6,10 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc && vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:ui": "vitest --ui"
   },
   "dependencies": {
     "@mantine/core": "^7.13.0",
@@ -17,10 +20,16 @@
     "react-dom": "^18.3.1"
   },
   "devDependencies": {
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/react": "^18.3.10",
     "@types/react-dom": "^18.3.0",
     "@vitejs/plugin-react": "^4.3.1",
+    "@vitest/ui": "^2.1.9",
+    "jsdom": "^29.1.1",
     "typescript": "^5.6.2",
-    "vite": "^5.4.8"
+    "vite": "^5.4.8",
+    "vitest": "^2.1.9"
   }
 }