feat: implement QuestionBank CRUD with pagination and template query

- Add pagination support to findAll (page, limit query params)
- Add findByTemplateId method to service
- Add GET /by-template/:templateId endpoint to controller
- Service already includes CRUD for QuestionBank and QuestionBankItem

server/src/knowledge-group/knowledge-group.entity.ts

@@ -0,0 +1,69 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  UpdateDateColumn,
+  ManyToMany,
+  JoinTable,
+  ManyToOne,
+  OneToMany,
+  JoinColumn,
+} from 'typeorm';
+import { KnowledgeBase } from '../knowledge-base/knowledge-base.entity';
+import { Tenant } from '../tenant/tenant.entity';
+
+@Entity('knowledge_groups')
+export class KnowledgeGroup {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column()
+  name: string;
+
+  @Column({ nullable: true })
+  description: string;
+
+  @Column({ default: '#3B82F6' })
+  color: string;
+
+  // Removed userId field to make groups globally accessible
+  // Tenant scoped: groups are shared within a tenant but isolated across tenants
+  @Column({ name: 'tenant_id', nullable: true, type: 'text' })
+  tenantId: string;
+
+  @ManyToOne(() => Tenant, { nullable: true, onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'tenant_id' })
+  tenant: Tenant;
+
+  // Hierarchical parent-child relationship
+  @Column({ name: 'parent_id', nullable: true, type: 'text' })
+  parentId: string | null;
+
+  @ManyToOne(() => KnowledgeGroup, (group) => group.children, {
+    nullable: true,
+    onDelete: 'SET NULL',
+  })
+  @JoinColumn({ name: 'parent_id' })
+  parent: KnowledgeGroup;
+
+  @OneToMany(() => KnowledgeGroup, (group) => group.parent)
+  children: KnowledgeGroup[];
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+
+  @UpdateDateColumn({ name: 'updated_at' })
+  updatedAt: Date;
+
+  @ManyToMany(() => KnowledgeBase, (kb) => kb.groups)
+  @JoinTable({
+    name: 'knowledge_base_groups',
+    joinColumn: { name: 'group_id', referencedColumnName: 'id' },
+    inverseJoinColumn: {
+      name: 'knowledge_base_id',
+      referencedColumnName: 'id',
+    },
+  })
+  knowledgeBases: KnowledgeBase[];
+}