feat: Implement offline-first Redux architecture with optimistic updates

Implemented comprehensive offline-first state management:

Redux Store Setup:
- Configure Redux Toolkit with @redux-offline/redux-offline
- Setup redux-persist with IndexedDB (localforage)
- Custom offline config with exponential backoff retry
- Normalized state with entity adapters

State Slices:
- activitiesSlice: Normalized activities with optimistic CRUD
- childrenSlice: Normalized children with optimistic CRUD
- networkSlice: Network status and connection quality
- offlineSlice: Sync queue and pending actions

Middleware:
- offlineMiddleware: Queue actions when offline
- syncMiddleware: Process pending actions when online
- Conflict resolution strategies (SERVER_WINS, CLIENT_WINS, LAST_WRITE_WINS, MERGE)
- Version-based conflict detection

Features:
- Optimistic updates for immediate UI feedback
- Automatic sync queue with retry logic (5 retries max)
- Network detection (browser events + periodic checks)
- Connection quality monitoring (excellent/good/poor/offline)
- Latency tracking
- Conflict resolution with multiple strategies
- Entity versioning for optimistic updates

Components:
- NetworkStatusIndicator: Full-screen status banner
- NetworkStatusBadge: Compact app bar badge
- ReduxProvider: Provider with network detection setup

Custom Hooks:
- useAppDispatch/useAppSelector: Typed Redux hooks
- useIsOnline: Check online status
- useHasPendingSync: Check for pending actions
- useSyncStatus: Get sync progress info
- useOptimisticAction: Combine optimistic + actual actions
- useNetworkQuality: Get connection quality
- useIsOptimistic: Check if entity is being synced

Documentation:
- Comprehensive README with usage examples
- Architecture overview
- Best practices guide
- Troubleshooting section

State Structure:
- Normalized entities with byId/allIds
- Optimistic metadata (_optimistic, _localId, _version)
- Entity adapters with memoized selectors
- Offline queue persistence to IndexedDB

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

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

maternal-web/package.json

@@ -21,11 +21,13 @@
     "@mui/icons-material": "^5.18.0",
     "@mui/material": "^5.18.0",
     "@mui/material-nextjs": "^7.3.2",
+    "@redux-offline/redux-offline": "^2.6.0",
     "@reduxjs/toolkit": "^2.9.0",
     "@tanstack/react-query": "^5.90.2",
     "axios": "^1.12.2",
     "date-fns": "^4.1.0",
     "framer-motion": "^11.18.2",
+    "localforage": "^1.10.0",
     "next": "14.2.0",
     "next-pwa": "^5.6.0",
     "react": "^18",