feat: scaffold matrix_client_pc (Wails + React-TS + mautrix-go + keyring)

Initial scaffold for issue 0147. App lives at
projects/element_agents/apps/matrix_client_pc/.

Deps:
- github.com/wailsapp/wails/v2 v2.11.0
- maunium.net/go/mautrix v0.25.2
- github.com/zalando/go-keyring v0.2.6

Next: MatrixService bindings + Login/Home React screens + helpers
(matrix_client_init, mas_oidc_loopback, keyring_token_store).

frontend/tsconfig.json

@@ -0,0 +1,31 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "useDefineForClassFields": true,
+    "lib": [
+      "DOM",
+      "DOM.Iterable",
+      "ESNext"
+    ],
+    "allowJs": false,
+    "skipLibCheck": true,
+    "esModuleInterop": false,
+    "allowSyntheticDefaultImports": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "module": "ESNext",
+    "moduleResolution": "Node",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true,
+    "jsx": "react-jsx"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "./tsconfig.node.json"
+    }
+  ]
+}