fix: Resolve black pages issue - Add missing auth slice and update checker

Fixed critical issues causing tracking pages to display black:
1. PWA service worker caching old JavaScript chunks
2. Missing auth Redux slice causing undefined errors

## Service Worker Update Checker
- Added /public/check-updates.js script
- Checks for SW updates every 60 seconds
- Auto-reloads page when new SW is activated
- Forces update check on page load
- Prevents future cache staleness issues

## Auth Redux Slice
- Created store/slices/authSlice.ts with User interface
- Added auth reducer to Redux store configuration
- Included auth in persist whitelist
- Provides selectors: selectUser, selectFamilyId, etc.
- Fixes "Cannot read properties of undefined (reading 'user')" error

## Root Cause
Tracking pages reference state.auth.user.familyId but auth slice
didn't exist in Redux store, causing TypeError on all tracking pages.

Build: ✅ PASSED
Files: 3 new, 2 modified

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

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

maternal-web/store/store.ts

@@ -4,6 +4,7 @@ import storage from 'redux-persist/lib/storage'; // defaults to localStorage for
 import { combineReducers } from '@reduxjs/toolkit';
 
 // Slices
+import authReducer from './slices/authSlice';
 import offlineReducer from './slices/offlineSlice';
 import activitiesReducer from './slices/activitiesSlice';
 import childrenReducer from './slices/childrenSlice';
@@ -19,10 +20,11 @@ const persistConfig = {
   version: 1,
   storage,
   // Only persist these slices (exclude network status as it should be fresh on reload)
-  whitelist: ['offline', 'activities', 'children'],
+  whitelist: ['auth', 'offline', 'activities', 'children'],
 };
 
 const rootReducer = combineReducers({
+  auth: authReducer,
   offline: offlineReducer,
   activities: activitiesReducer,
   children: childrenReducer,