Add Ping frontend

React 19 + TypeScript client built with Vite. Zustand for local state,
react-oidc-context for the login flow, a SignalR connection for chat and
presence events, and LiveKit's React components for voice/video calls.

frontend/tsconfig.app.json

@@ -0,0 +1,26 @@
+{
+  "compilerOptions": {
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.app.tsbuildinfo",
+    "target": "es2023",
+    "lib": ["ES2023", "DOM"],
+    "module": "esnext",
+    "types": ["vite/client"],
+    "allowArbitraryExtensions": true,
+    "skipLibCheck": true,
+
+    /* Bundler mode */
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "moduleDetection": "force",
+    "noEmit": true,
+    "jsx": "react-jsx",
+
+    /* Linting */
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "erasableSyntaxOnly": true,
+    "noFallthroughCasesInSwitch": true
+  },
+  "include": ["src"]
+}