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/components/providers/ReduxProvider.tsx

@@ -2,8 +2,10 @@
 
 import { useEffect, useRef } from 'react';
 import { Provider } from 'react-redux';
-import { store } from '@/store/store';
+import { PersistGate } from 'redux-persist/integration/react';
+import { store, persistor } from '@/store/store';
 import { setupNetworkDetection } from '@/store/middleware/offlineMiddleware';
+import { CircularProgress, Box } from '@mui/material';
 
 export function ReduxProvider({ children }: { children: React.ReactNode }) {
   const cleanupRef = useRef<(() => void) | null>(null);
@@ -20,5 +22,25 @@ export function ReduxProvider({ children }: { children: React.ReactNode }) {
     };
   }, []);
 
-  return <Provider store={store}>{children}</Provider>;
+  return (
+    <Provider store={store}>
+      <PersistGate
+        loading={
+          <Box
+            sx={{
+              display: 'flex',
+              justifyContent: 'center',
+              alignItems: 'center',
+              minHeight: '100vh'
+            }}
+          >
+            <CircularProgress />
+          </Box>
+        }
+        persistor={persistor}
+      >
+        {children}
+      </PersistGate>
+    </Provider>
+  );
 }