feat: implement Phase 2 (Go Agent) and Phase 3 (React Frontend MVP)

Phase 2 - Go Agent Core:
- gRPC client with exponential backoff reconnect logic
- Command executor (PowerShell/sh cross-platform)
- Proto stubs regenerated with module= option (correct output path)
- gRPC upgraded to v1.79.3 (BidiStreamingClient support)

Phase 3 - React Frontend MVP:
- Vite + React 18 + TypeScript setup with Tailwind CSS v4
- TanStack Query for data fetching, API client + TypeScript types
- Dashboard page: stats cards (agents/status/tickets) + sortable agents table
- Agent detail page: CPU/RAM charts (Recharts), disk usage, shell command executor
- Tickets page: CRUD with modals, filters, sortable table
- Dark mode with CSS custom properties

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

Frontend/package.json

@@ -0,0 +1,47 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "lint": "eslint .",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@microsoft/signalr": "^10.0.0",
+    "@radix-ui/react-dialog": "^1.1.15",
+    "@radix-ui/react-dropdown-menu": "^2.1.16",
+    "@radix-ui/react-select": "^2.2.6",
+    "@radix-ui/react-separator": "^1.1.8",
+    "@radix-ui/react-slot": "^1.2.4",
+    "@radix-ui/react-tabs": "^1.1.13",
+    "@radix-ui/react-tooltip": "^1.2.8",
+    "@tailwindcss/vite": "^4.2.2",
+    "@tanstack/react-query": "^5.91.2",
+    "@tanstack/react-router": "^1.167.5",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
+    "lucide-react": "^0.577.0",
+    "react": "^19.2.4",
+    "react-dom": "^19.2.4",
+    "recharts": "^3.8.0",
+    "tailwind-merge": "^3.5.0",
+    "tailwindcss": "^4.2.2"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.39.4",
+    "@types/node": "^24.12.0",
+    "@types/react": "^19.2.14",
+    "@types/react-dom": "^19.2.3",
+    "@vitejs/plugin-react": "^6.0.1",
+    "eslint": "^9.39.4",
+    "eslint-plugin-react-hooks": "^7.0.1",
+    "eslint-plugin-react-refresh": "^0.5.2",
+    "globals": "^17.4.0",
+    "typescript": "~5.9.3",
+    "typescript-eslint": "^8.57.0",
+    "vite": "^8.0.1"
+  }
+}