Add complete GraphQL mutation support for activity tracking and child management:
**Activity Mutations:**
- createActivity: Create new activities (feeding, sleep, diaper, medication)
- updateActivity: Update existing activities
- deleteActivity: Delete activities
**Child Mutations:**
- createChild: Add new children to families
- updateChild: Update child information
- deleteChild: Soft delete children
**Implementation Details:**
- Created GraphQL input types (CreateActivityInput, UpdateActivityInput, CreateChildInput, UpdateChildInput)
- Implemented ActivityResolver with full CRUD mutations
- Implemented ChildResolver with full CRUD mutations
- Registered resolvers in GraphQL module with TrackingService and ChildrenService
- Auto-generated GraphQL schema with all mutations
- All mutations protected with GqlAuthGuard for authentication
- Support for JSON metadata fields and Gender enum
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
