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/lib/api/tracking.ts

@@ -44,19 +44,44 @@ export const trackingApi = {
     if (endDate) params.endDate = endDate;
 
     const response = await apiClient.get('/api/v1/activities', { params });
-    return response.data.data.activities;
+    // Transform backend response to frontend format
+    const activities = response.data.data.activities.map((activity: any) => ({
+      ...activity,
+      timestamp: activity.startedAt, // Frontend expects timestamp
+      data: activity.metadata,        // Frontend expects data
+    }));
+    return activities;
   },
 
   // Get a specific activity
   getActivity: async (id: string): Promise<Activity> => {
     const response = await apiClient.get(`/api/v1/activities/${id}`);
-    return response.data.data.activity;
+    const activity = response.data.data.activity;
+    // Transform backend response to frontend format
+    return {
+      ...activity,
+      timestamp: activity.startedAt,
+      data: activity.metadata,
+    };
   },
 
   // Create a new activity
   createActivity: async (childId: string, data: CreateActivityData): Promise<Activity> => {
-    const response = await apiClient.post(`/api/v1/activities?childId=${childId}`, data);
-    return response.data.data.activity;
+    // Transform frontend data structure to backend DTO format
+    const payload = {
+      type: data.type,
+      startedAt: data.timestamp, // Backend expects startedAt, not timestamp
+      metadata: data.data,        // Backend expects metadata, not data
+      notes: data.notes,
+    };
+    const response = await apiClient.post(`/api/v1/activities?childId=${childId}`, payload);
+    const activity = response.data.data.activity;
+    // Transform backend response to frontend format
+    return {
+      ...activity,
+      timestamp: activity.startedAt,
+      data: activity.metadata,
+    };
   },
 
   // Update an activity