feat: initialize app with routing, query management, and UI framework

- Replace Vite boilerplate with React Router for page navigation
- Add React Query for server state and cache management
- Integrate shadcn/ui component library with Tailwind CSS v4
- Configure @/ path alias for clean module imports
- Set up Vite dev proxy to API backend
- Remove default App.css, App.tsx, and react.svg assets

tsconfig.json

@@ -18,7 +18,13 @@
     "strict": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "noFallthroughCasesInSwitch": true
+    "noFallthroughCasesInSwitch": true,
+
+    /* Path aliases */
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"]
+    }
   },
   "include": ["src"],
   "references": [{ "path": "./tsconfig.node.json" }]