feat: add certificates, groups, support system, and moderation

Backend changes:
- Add Certificate generation service with beautiful HTML templates
- Add CourseGroup, GroupMember, GroupMessage models for group collaboration
- Add Homework and HomeworkSubmission models with AI + teacher grading
- Add SupportTicket and TicketMessage models for help desk
- Add Moderation API for admin/moderator course approval workflow
- All new modules: CertificatesModule, GroupsModule, SupportModule, ModerationModule

Frontend changes:
- Add certificate download button when course completed
- Update course page to load enrollment progress from backend
- Integrate lesson completion with backend API

Database schema now supports:
- Course groups with chat functionality
- Homework assignments with dual AI/human grading
- Support ticket system with admin responses
- Full moderation workflow (PENDING_REVIEW -> PUBLISHED/REJECTED)

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/app.module.ts

@@ -7,6 +7,10 @@ import { UsersModule } from './users/users.module';
 import { CoursesModule } from './courses/courses.module';
 import { CatalogModule } from './catalog/catalog.module';
 import { EnrollmentModule } from './enrollment/enrollment.module';
+import { CertificatesModule } from './certificates/certificates.module';
+import { GroupsModule } from './groups/groups.module';
+import { SupportModule } from './support/support.module';
+import { ModerationModule } from './moderation/moderation.module';
 import { GenerationModule } from './generation/generation.module';
 import { PaymentsModule } from './payments/payments.module';
 import { SearchModule } from './search/search.module';
@@ -42,6 +46,10 @@ import { PrismaModule } from './common/prisma/prisma.module';
     CoursesModule,
     CatalogModule,
     EnrollmentModule,
+    CertificatesModule,
+    GroupsModule,
+    SupportModule,
+    ModerationModule,
     GenerationModule,
     PaymentsModule,
     SearchModule,