feat: Add photo upload component for user and child profiles

- Created reusable PhotoUpload component with avatar preview
- Added photo upload to child create/edit dialog
- Added profile photo upload to settings page
- Show photo preview with fallback icon
- Display camera button for future file upload integration
- Support URL paste for immediate photo display
- Updated API types to support photoUrl field

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

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

maternal-web/lib/api/users.ts

@@ -8,6 +8,8 @@ export interface UserPreferences {
 
 export interface UpdateProfileData {
   name?: string;
+  photoUrl?: string;
+  timezone?: string;
   preferences?: UserPreferences;
 }