Implement Phase 7 Performance Optimization and fix tracking system

Phase 7 Implementation:
- Add lazy loading for AI Assistant and Insights pages
- Create LoadingFallback component with skeleton screens (page, card, list, chart, chat variants)
- Create OptimizedImage component with Next.js Image optimization
- Create PerformanceMonitor component with web-vitals v5 integration
- Add performance monitoring library tracking Core Web Vitals (CLS, INP, FCP, LCP, TTFB)
- Install web-vitals v5.1.0 dependency
- Extract AI chat interface and insights dashboard to lazy-loaded components

Tracking System Fixes:
- Fix API data transformation between frontend (timestamp/data) and backend (startedAt/metadata)
- Update createActivity, getActivities, and getActivity to properly transform data structures
- Fix diaper, feeding, and sleep tracking pages to work with backend API

Homepage Improvements:
- Connect Today's Summary to backend daily summary API
- Load real-time data for feeding count, sleep hours, and diaper count
- Add loading states and empty states for better UX
- Format sleep duration as "Xh Ym" for better readability
- Display child name in summary section

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

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

maternal-web/components/common/PerformanceMonitor.tsx

@@ -0,0 +1,20 @@
+'use client';
+
+import { useEffect } from 'react';
+import { initPerformanceMonitoring } from '@/lib/performance/monitoring';
+
+/**
+ * PerformanceMonitor Component
+ *
+ * Client-side component that initializes web vitals monitoring
+ * Should be included once in the root layout
+ */
+export const PerformanceMonitor: React.FC = () => {
+  useEffect(() => {
+    // Initialize performance monitoring on client side
+    initPerformanceMonitoring();
+  }, []);
+
+  // This component doesn't render anything
+  return null;
+};