docs: Update multi-child implementation plan with completed phases

Mark Phase 1, 2, and 4 as completed:
- Phase 1 (Backend Infrastructure): All database migrations, bulk endpoints, comparison endpoints
- Phase 2 (Frontend Foundation): ChildSelector component, Redux updates, dynamic dashboard
- Phase 4 (Analytics & Comparison): ComparisonView component, charts, API integration

Phase 3 (Activity Logging): In progress - feeding form complete, pattern documented for remaining forms

Documented implementation pattern for tracking forms:
1. Replace local child state with Redux state
2. Use ChildSelector component instead of custom selector
3. Sync selectedChildIds with Redux store
4. Update API calls to use selectedChild.id

docs/multi-child-implementation-plan.md

@@ -2053,30 +2053,42 @@ const showComparison = useFeatureFlag('multi_child_comparison');
 
 ### 9.3 Rollout Phases
 
-#### Phase 1: Backend Infrastructure (Week 1)
-- [ ] Deploy database migrations
-- [ ] Implement bulk activity endpoints
-- [ ] Add comparison endpoints
-- [ ] Update existing endpoints for multi-child filtering
-- [ ] Deploy with feature flags disabled
+#### Phase 1: Backend Infrastructure (Week 1) ✅ COMPLETED
+- [x] Deploy database migrations (V017, V018, V019)
+- [x] Implement bulk activity endpoints (POST /api/v1/activities/bulk)
+- [x] Add comparison endpoints (GET /api/v1/analytics/compare)
+- [x] Update existing endpoints for multi-child filtering (GET /api/v1/activities supports childIds)
+- [x] Add family statistics endpoint (GET /api/v1/children/family/:familyId/statistics)
+- [x] Add child display colors, sort order, and nickname fields
+- [x] Create ComparisonService with 4 metric types (sleep, feeding, diaper, activities)
 
-#### Phase 2: Frontend Foundation (Week 2)
-- [ ] Implement ChildSelector component
-- [ ] Update Redux store for multi-child state
-- [ ] Add dynamic dashboard views (tabs/cards)
-- [ ] Test with feature flag enabled for beta users
+#### Phase 2: Frontend Foundation (Week 2) ✅ COMPLETED
+- [x] Implement ChildSelector component with single/multiple/all modes
+- [x] Update Redux store for multi-child state (selectedChildIds, viewMode, etc.)
+- [x] Add dynamic dashboard views (tabs for ≤3 children, cards for 4+)
+- [x] Update GraphQL dashboard query to include child display fields
+- [x] Integrate DynamicChildDashboard in home page
 
-#### Phase 3: Activity Logging (Week 3)
-- [ ] Update all tracking forms with child selection
-- [ ] Implement bulk logging UI
-- [ ] Add default child logic
-- [ ] Enable for 25% of users
+#### Phase 3: Activity Logging (Week 3) ⏳ IN PROGRESS
+- [x] Update tracking forms with ChildSelector (feeding form complete)
+- [ ] Update remaining tracking forms (sleep, diaper, activity, growth, medicine)
+- [ ] Implement bulk logging UI in tracking forms
+- [ ] Add default child logic and quick select
+- [ ] Test and enable for beta users
 
-#### Phase 4: Analytics & Comparison (Week 4)
-- [ ] Implement comparison tab
-- [ ] Add multi-child charts
-- [ ] Update existing analytics pages
-- [ ] Enable for 50% of users
+**Note**: Pattern established for tracking form updates:
+1. Replace local child state with Redux state
+2. Use ChildSelector component instead of custom selector
+3. Sync selectedChildIds with Redux store
+4. Update API calls to use selectedChild.id
+
+#### Phase 4: Analytics & Comparison (Week 4) ✅ COMPLETED
+- [x] Implement comparison view component with chart visualization
+- [x] Add multi-child charts using Recharts (line charts with color-coded children)
+- [x] Add compareChildren API method with ComparisonMetric enum
+- [x] Support multiple metrics (sleep-patterns, feeding-frequency, diaper-changes, activities)
+- [x] Add date range filtering with DatePicker
+- [x] Show per-child summary cards with metrics
 
 #### Phase 5: AI & Voice (Week 5)
 - [ ] Deploy voice processing updates