feat: US-003 — electron-trpc IPC bridge and appRouter scaffold

- Install electron-trpc, @trpc/server, @trpc/client, @trpc/react-query, @tanstack/react-query, zod
- Create appRouter in src/main/router/index.ts with stub routers for: health, clients, projects, tasks, checkpoints, notes, ai
- health.ping procedure returns 'pong'
- All procedure inputs validated with Zod schemas
- Configure IPC handler in main process (createIPCHandler) and preload (exposeElectronTRPC)
- Create renderer trpc client in src/renderer/lib/trpc.ts with ipcLink
- Wrap app with TRPCProvider + QueryClientProvider in src/renderer/index.tsx
- Verify health.ping in HomePage component (shows 'tRPC IPC bridge: pong')
- Typecheck passes

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

package.json

@@ -44,16 +44,22 @@
     "vite": "^5.4.21"
   },
   "dependencies": {
+    "@tanstack/react-query": "^5.90.21",
     "@tanstack/react-router": "^1.161.1",
+    "@trpc/client": "^11.10.0",
+    "@trpc/react-query": "^11.10.0",
+    "@trpc/server": "^11.10.0",
     "better-sqlite3": "^12.6.2",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "drizzle-orm": "^0.45.1",
     "electron-squirrel-startup": "^1.0.1",
+    "electron-trpc": "^0.7.1",
     "framer-motion": "^12.34.2",
     "lucide-react": "^0.575.0",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
-    "tailwind-merge": "^3.5.0"
+    "tailwind-merge": "^3.5.0",
+    "zod": "^4.3.6"
   }
 }