feat: ticketing system with technical/sales roles and department routing

Backend:
- Added TECHNICAL and SALES roles to UserRole enum
- Added TicketDepartment, TicketStatus, TicketPriority enums
- Created Ticket and TicketMessage entities with relationships
- Created TicketsModule with full CRUD service and controller
- Ticket routing: users create tickets to technical/sales departments
- Staff reply updates status (answered), user reply sets waiting
- Role-based access: technical staff sees technical tickets, sales sees sales tickets
- Admin sees all tickets with stats (total, open, avg response time)
- Updated access control: technical role has admin-level access (except role change)
- Sales role can view users and handle sales tickets
- Clusters controller: technical role can manage clusters/pools
- Users controller: technical/sales can view users, only admin changes roles

Frontend:
- New user ticket pages: list (with create form) + detail (chat-style messages)
- Staff ticket panel: filtered by department with status filters
- Admin all-tickets page with statistics dashboard and department/status filters
- Updated sidebar: role-based nav items (admin/technical/sales sections)
- Role badges in header for technical (blue) and sales (green)
- Admin users page: new roles in dropdowns, role change restricted to admin only
- Deploy page: technical role gets cluster selection access like admin

backend/src/app.module.ts

@@ -9,6 +9,7 @@ import { DeploymentsModule } from './deployments/deployments.module';
 import { ClustersModule } from './clusters/clusters.module';
 import { KubernetesModule } from './kubernetes/kubernetes.module';
 import { BuildModule } from './build/build.module';
+import { TicketsModule } from './tickets/tickets.module';
 import configuration from './config/configuration';
 
 @Module({
@@ -56,6 +57,7 @@ import configuration from './config/configuration';
     ClustersModule,
     KubernetesModule,
     BuildModule,
+    TicketsModule,
   ],
 })
 export class AppModule {}