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/notifications-config.entity.ts

@@ -0,0 +1,60 @@
+import { Entity, PrimaryGeneratedColumn, Column, ManyToOne, JoinColumn } from 'typeorm';
+import { License } from './license.entity';
+
+@Entity('notifications_config')
+export class NotificationsConfig {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ type: 'uuid', unique: true })
+  license_id: string;
+
+  @Column({ type: 'text', nullable: true })
+  discord_webhook_url: string | null;
+
+  @Column({ type: 'boolean', default: false })
+  discord_enabled: boolean;
+
+  @Column({ type: 'text', nullable: true })
+  pushbullet_api_key: string | null;
+
+  @Column({ type: 'boolean', default: false })
+  pushbullet_enabled: boolean;
+
+  @Column({ type: 'boolean', default: false })
+  email_enabled: boolean;
+
+  @Column({ type: 'text', nullable: true })
+  email_address: string | null;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_start: boolean;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_stop: boolean;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_crash: boolean;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_wipe_start: boolean;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_wipe_complete: boolean;
+
+  @Column({ type: 'boolean', default: true })
+  notify_on_wipe_failure: boolean;
+
+  @Column({ type: 'boolean', default: false })
+  notify_on_player_threshold: boolean;
+
+  @Column({ type: 'int', nullable: true })
+  player_threshold: number | null;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  created_at: Date;
+
+  @ManyToOne(() => License, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'license_id' })
+  license: License;
+}