feat: Implement GraphQL API with optimized dashboard queries

Implemented complete GraphQL API with Apollo Server for efficient data fetching:

Backend Changes:
- Installed @nestjs/graphql@13.2.0, @nestjs/apollo@13.2.1, graphql@16.11.0, dataloader@2.2.3
- Configured Apollo Server with auto schema generation (src/schema.gql)
- GraphQL Playground enabled in non-production environments
- JWT authentication via GqlAuthGuard
- Custom error formatting

GraphQL Types (src/graphql/types/):
- UserType with family relationships
- ChildType with birthDate, gender, photoUrl
- FamilyMemberType with role and user relation
- ActivityGQLType with startedAt, endedAt, metadata
- DashboardType aggregating all dashboard data
- DailySummaryType with activity counts and totals
- Enum types: ActivityType, FamilyRole, Gender, FeedingMethod, DiaperType

Dashboard Resolver (src/graphql/resolvers/dashboard.resolver.ts):
- Query: dashboard(childId?: ID) returns DashboardType
- Single optimized query replacing 4+ REST API calls:
  * GET /api/v1/children
  * GET /api/v1/tracking/child/:id/recent
  * GET /api/v1/tracking/child/:id/summary/today
  * GET /api/v1/families/:id/members
- Aggregates children, activities, family members, summaries in one query
- ResolveField decorators for child and logger relations
- Calculates daily summary (feeding, sleep, diaper, medication counts)
- Uses Between for date range filtering
- Handles metadata extraction for activity details

DataLoader Implementation (src/graphql/dataloaders/):
- ChildDataLoader: batchChildren, batchChildrenByFamily
- UserDataLoader: batchUsers
- REQUEST scope for per-request instance
- Prevents N+1 query problem when resolving relations
- Uses TypeORM In() for batch loading

GraphQL Module (src/graphql/graphql.module.ts):
- Exports ChildDataLoader and UserDataLoader
- TypeORM integration with Child, Activity, FamilyMember, User entities
- DashboardResolver provider

Example Queries (src/graphql/example-queries.gql):
- GetDashboard with childId parameter
- GetDashboardAllChildren for listing
- Documented usage and expected results

Files Created (11 total):
- src/graphql/types/ (5 files)
- src/graphql/dataloaders/ (2 files)
- src/graphql/resolvers/ (1 file)
- src/graphql/guards/ (1 file)
- src/graphql/graphql.module.ts
- src/graphql/example-queries.gql

Performance Improvements:
- Dashboard load reduced from 4+ REST calls to 1 GraphQL query
- DataLoader batching eliminates N+1 queries
- Client can request only needed fields
- Reduced network overhead and latency

Usage:
- Endpoint: http://localhost:3020/graphql
- Playground: http://localhost:3020/graphql (dev only)
- Authentication: JWT token in Authorization header

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

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

docs/implementation-gaps.md

@@ -86,7 +86,7 @@ This document identifies features specified in the documentation that are not ye
 5. **Security Hardening** - CORS configuration, comprehensive input validation, XSS headers
 
 **Medium Priority (Post-Launch)**:
-1. **GraphQL API** - Complex queries for dashboard optimization
+1. ~~**GraphQL API**~~ - ✅ COMPLETED (October 2, 2025) - Complex queries for dashboard optimization with DataLoader for N+1 prevention
 2. **Voice Processing** - Whisper API integration, multi-language voice recognition
 3. **Analytics & Predictions** - Pattern detection, ML-based next event predictions
 4. **PWA Features** - Service worker configuration, offline pages, install prompts
@@ -159,27 +159,75 @@ This document identifies features specified in the documentation that are not ye
    - Priority: High
    - Impact: Account security and COPPA compliance
 
-### 1.2 GraphQL Implementation (MEDIUM Priority)
+### 1.2 GraphQL Implementation ✅ COMPLETED (October 2, 2025)
 
 **Source**: `maternal-app-api-spec.md`, `maternal-app-tech-stack.md`
 
-1. **GraphQL Endpoint**
-   - Status: Dependencies installed (@nestjs/graphql) but not configured
-   - Current: REST API only
-   - Needed: GraphQL endpoint at /graphql with schema
-   - Priority: Medium
-   - Impact: Efficient complex data fetching for dashboard
+1. **GraphQL Endpoint** ✅ COMPLETED
+   - Status: **IMPLEMENTED**
+   - Current: GraphQL endpoint at /graphql with auto-generated schema
+   - Implemented:
+     * **Apollo Server Integration** (app.module.ts:35-57):
+       - ApolloDriver with @nestjs/apollo@13.2.1
+       - Auto schema generation at src/schema.gql
+       - GraphQL Playground enabled in non-production
+       - JWT authentication via GqlAuthGuard
+       - Custom error formatting
+     * **GraphQL Types** (src/graphql/types/):
+       - UserType, ChildType, FamilyMemberType, ActivityGQLType
+       - DashboardType with DailySummaryType
+       - Enum types: ActivityType, FamilyRole, Gender, FeedingMethod, DiaperType
+       - All types with proper Field decorators
+     * **Dashboard Resolver** (dashboard.resolver.ts):
+       - Query: dashboard(childId?: ID) returns DashboardType
+       - Single optimized query replacing 4+ REST endpoints
+       - Aggregates children, activities, family members, summaries
+       - ResolveField for child and logger relations
+       - Calculates daily summary (feeding, sleep, diaper, medication counts)
+     * **DataLoader for N+1 Prevention** (src/graphql/dataloaders/):
+       - ChildDataLoader: batchChildren, batchChildrenByFamily
+       - UserDataLoader: batchUsers
+       - REQUEST scope for per-request batching
+       - Prevents N+1 query problem for relations
+     * **GraphQL Module** (graphql.module.ts):
+       - Exports DataLoaders for dependency injection
+       - TypeORM integration with Child, Activity, FamilyMember, User
+       - DashboardResolver provider
+   - Files Created:
+     * src/graphql/types/ (5 files: user, child, family, activity, dashboard)
+     * src/graphql/dataloaders/ (2 files: child, user)
+     * src/graphql/resolvers/ (1 file: dashboard)
+     * src/graphql/guards/ (1 file: gql-auth)
+     * src/graphql/graphql.module.ts
+     * src/graphql/example-queries.gql
+   - Example Query:
+     ```graphql
+     query GetDashboard($childId: ID) {
+       dashboard(childId: $childId) {
+         children { id name birthDate }
+         selectedChild { id name }
+         recentActivities { id type startedAt logger { name } }
+         todaySummary { feedingCount sleepCount diaperCount }
+         familyMembers { userId role user { name } }
+         totalChildren
+         totalActivitiesToday
+       }
+     }
+     ```
+   - Performance: Single query replaces 4+ REST calls
+   - Priority: Medium ✅ **COMPLETE**
+   - Impact: Dashboard load time reduced, efficient data fetching
 
 2. **GraphQL Subscriptions**
    - Status: Not implemented
-   - Current: WebSocket for real-time sync
+   - Current: WebSocket for real-time sync (Socket.io)
    - Needed: GraphQL subscriptions for real-time data
-   - Priority: Low
+   - Priority: Low (deferred - Socket.io working well)
    - Impact: Alternative real-time implementation
 
-3. **Complex Dashboard Queries**
-   - Status: Not implemented
-   - Current: Multiple REST calls for dashboard data
+3. **Complex Dashboard Queries** ✅ COMPLETED
+   - Status: **IMPLEMENTED via GraphQL dashboard query**
+   - Current: Single GraphQL query aggregates all dashboard data
    - Needed: Single GraphQL query for entire dashboard
    - Priority: Medium
    - Impact: Performance optimization, reduced API calls