Add property manager UI with json-server backend

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

package.json

@@ -7,13 +7,16 @@
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.2",
     "@testing-library/user-event": "^13.5.0",
+    "concurrently": "^10.0.3",
+    "json-server": "^1.0.0-beta.15",
     "react": "^19.2.7",
     "react-dom": "^19.2.7",
     "react-scripts": "5.0.1",
     "web-vitals": "^2.1.4"
   },
+  "proxy": "http://localhost:3001",
   "scripts": {
-    "start": "react-scripts start",
+    "start": "concurrently \"json-server --watch db.json --port 3001\" \"react-scripts start\"",
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject"