fix: Align NestJS entity columns with service expectations

Resolved 12 TypeScript compilation errors caused by mismatched column names between TypeORM entities and service layer.

Entity changes:
- NotificationsConfig: Renamed email_alerts_enabled → email_enabled, added email_address, standardized notification event column names (notify_on_start, notify_on_stop, notify_on_crash, etc.)
- ScheduledTask: Renamed is_active → is_enabled, added last_run timestamp
- TeamMember: Renamed accepted_at → joined_at to match service expectations
- Role: Added description column for custom role metadata

Service changes:
- JwtStrategy: Updated to reference joined_at instead of accepted_at

All services now compile cleanly against updated entity schemas.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/entities/role.entity.ts

@@ -0,0 +1,37 @@
+import { Entity, PrimaryGeneratedColumn, Column, ManyToOne, JoinColumn } from 'typeorm';
+import { License } from './license.entity';
+
+@Entity('roles')
+export class Role {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ type: 'uuid', nullable: true })
+  license_id: string | null;
+
+  @Column({ type: 'varchar', length: 50 })
+  role_name: string;
+
+  @Column({ type: 'text', nullable: true })
+  description: string | null;
+
+  @Column({ type: 'boolean', default: false })
+  is_system_default: boolean;
+
+  @Column({ type: 'uuid', nullable: true })
+  is_cloned_from: string | null;
+
+  @Column({ type: 'jsonb', default: {} })
+  permissions: Record<string, any>;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  created_at: Date;
+
+  @ManyToOne(() => License, { onDelete: 'CASCADE', nullable: true })
+  @JoinColumn({ name: 'license_id' })
+  license: License | null;
+
+  @ManyToOne(() => Role, { onDelete: 'SET NULL', nullable: true })
+  @JoinColumn({ name: 'is_cloned_from' })
+  cloned_from: Role | null;
+}