feat(rfa): complete RFA Approval Refactor - all 9 phases (T001-T080)

Phase 1-2: Setup, SQL schema, enums, queue constants, base entities
Phase 3 (US1): ReviewTeam, ReviewTeamMember, ReviewTask, TaskCreationService
Phase 4 (US2): ResponseCode, ResponseCodeRule, ImplicationsService, NotificationTriggerService
Phase 5 (US3): Delegation entity, CircularDetectionService, DelegationService/Controller/Module
Phase 6 (US4): ReminderRule, SchedulerService, EscalationService, ReminderProcessor, ReminderModule
Phase 7 (US5): DistributionMatrix, DistributionRecipient, ApprovalListenerService (Strangler),
               TransmittalCreatorService, DistributionProcessor, DistributionModule
Phase 8 (US6): MatrixManagementService, InheritanceService (global→project override)
Phase 9 (Polish): AggregateStatusService, ConsensusService, VetoOverrideService,
                  ParallelGatewayHandler, review-validators, optimistic locking in completeReview,
                  test stubs (unit/integration/e2e), jest.config.js updated for tests/ directory

Frontend: ReviewTaskInbox, ParallelProgress, VetoOverrideDialog, DelegationForm,
          DelegatedBadge, MatrixEditor, ProjectOverrideManager, DistributionStatus,
          ReminderHistory, ResponseCodeSelector, CodeImplications, CompleteReviewForm,
          ReviewTeamForm, ReviewTeamSelector, TeamMemberManager

Closes #1

backend/src/modules/delegation/entities/delegation.entity.ts

@@ -0,0 +1,67 @@
+// File: src/modules/delegation/entities/delegation.entity.ts
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  UpdateDateColumn,
+  ManyToOne,
+  JoinColumn,
+} from 'typeorm';
+import { Exclude } from 'class-transformer';
+import { UuidBaseEntity } from '../../../common/entities/uuid-base.entity';
+import { User } from '../../user/entities/user.entity';
+import { DelegationScope } from '../../common/enums/review.enums';
+
+@Entity('delegations')
+export class Delegation extends UuidBaseEntity {
+  @PrimaryGeneratedColumn()
+  @Exclude()
+  id!: number;
+
+  @Column({ name: 'delegator_user_id' })
+  @Exclude()
+  delegatorUserId!: number; // ผู้มอบหมาย (A)
+
+  @Column({ name: 'delegate_user_id' })
+  @Exclude()
+  delegateUserId!: number; // ผู้รับมอบหมาย (B)
+
+  @Column({
+    type: 'enum',
+    enum: DelegationScope,
+    default: DelegationScope.ALL,
+  })
+  scope!: DelegationScope;
+
+  @Column({ name: 'project_id', nullable: true })
+  @Exclude()
+  projectId?: number; // NULL = all projects (ถ้า scope = PROJECT)
+
+  @Column({ name: 'start_date', type: 'date' })
+  startDate!: Date;
+
+  @Column({ name: 'end_date', type: 'date' })
+  endDate!: Date;
+
+  @Column({ type: 'text', nullable: true })
+  reason?: string;
+
+  @Column({ name: 'is_active', type: 'tinyint', default: 1 })
+  isActive!: boolean;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt!: Date;
+
+  @UpdateDateColumn({ name: 'updated_at' })
+  updatedAt!: Date;
+
+  // Relations
+  @ManyToOne(() => User)
+  @JoinColumn({ name: 'delegator_user_id' })
+  delegator?: User;
+
+  @ManyToOne(() => User)
+  @JoinColumn({ name: 'delegate_user_id' })
+  delegate?: User;
+}