Add backend API integration for Children, Family, and Tracking

API Services Created:
- lib/api/children.ts: Full CRUD operations for children management
- lib/api/families.ts: Family member management and invitations
- lib/api/tracking.ts: Activity tracking (feeding, sleep, diaper, etc.)

Children Page Implementation:
- Fetch and display children from backend API
- Add/Edit child with modal dialog (ChildDialog component)
- Delete child with confirmation (DeleteConfirmDialog component)
- Age calculation from birthDate
- Loading states and error handling
- Responsive card grid layout
- Gender-based avatar colors
- Empty state for no children

AuthContext Updates:
- Added families array to User interface
- Includes familyId for API calls

Components:
- components/children/ChildDialog.tsx: Form for add/edit child
- components/children/DeleteConfirmDialog.tsx: Delete confirmation

All components use Material-UI theme and include proper TypeScript types

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

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

maternal-web/lib/api/families.ts

@@ -0,0 +1,69 @@
+import apiClient from './client';
+
+export interface Family {
+  id: string;
+  name: string;
+  shareCode: string;
+  createdBy: string;
+  subscriptionTier: string;
+  members?: FamilyMember[];
+}
+
+export interface FamilyMember {
+  id: string;
+  userId: string;
+  familyId: string;
+  role: 'parent' | 'caregiver' | 'viewer';
+  permissions: any;
+  user?: {
+    id: string;
+    name: string;
+    email: string;
+  };
+}
+
+export interface InviteMemberData {
+  email: string;
+  role: 'parent' | 'caregiver' | 'viewer';
+}
+
+export interface JoinFamilyData {
+  shareCode: string;
+}
+
+export const familiesApi = {
+  // Get a specific family
+  getFamily: async (familyId: string): Promise<Family> => {
+    const response = await apiClient.get(`/api/v1/families/${familyId}`);
+    return response.data.data.family;
+  },
+
+  // Get family members
+  getFamilyMembers: async (familyId: string): Promise<FamilyMember[]> => {
+    const response = await apiClient.get(`/api/v1/families/${familyId}/members`);
+    return response.data.data.members;
+  },
+
+  // Invite a family member
+  inviteMember: async (familyId: string, data: InviteMemberData): Promise<any> => {
+    const response = await apiClient.post(`/api/v1/families/invite?familyId=${familyId}`, data);
+    return response.data.data.invitation;
+  },
+
+  // Join a family using share code
+  joinFamily: async (data: JoinFamilyData): Promise<FamilyMember> => {
+    const response = await apiClient.post('/api/v1/families/join', data);
+    return response.data.data.member;
+  },
+
+  // Update member role
+  updateMemberRole: async (familyId: string, userId: string, role: string): Promise<FamilyMember> => {
+    const response = await apiClient.patch(`/api/v1/families/${familyId}/members/${userId}/role`, { role });
+    return response.data.data.member;
+  },
+
+  // Remove a family member
+  removeMember: async (familyId: string, userId: string): Promise<void> => {
+    await apiClient.delete(`/api/v1/families/${familyId}/members/${userId}`);
+  },
+};