Implement Redux Persist for state persistence across page reloads

- Install redux-persist package
- Configure persistReducer with whitelist (offline, activities, children)
- Exclude network slice from persistence (should be fresh on reload)
- Add PersistGate to ReduxProvider with loading indicator
- Configure serializableCheck to ignore persist actions
- Store state now persists to localStorage automatically

This fixes the issue where app state was lost on page reload, improving UX.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/package.json

@@ -32,8 +32,11 @@
     "react": "^18",
     "react-dom": "^18",
     "react-hook-form": "^7.63.0",
+    "react-markdown": "^10.1.0",
     "react-redux": "^9.2.0",
     "recharts": "^3.2.1",
+    "redux-persist": "^6.0.0",
+    "remark-gfm": "^4.0.1",
     "socket.io-client": "^4.8.1",
     "web-vitals": "^5.1.0",
     "workbox-webpack-plugin": "^7.3.0",