feat: 考核系统升级 P0+P1+P2 — 体验/题库/配置增强

P0 — 答题体验优化:
- 题序导航点：题目进度可视化，标记题目标记
- 标记回头检查: 点击🏷️按钮标记当前题，导航点变黄色
- 提交确认弹窗: 未答完时提交弹出确认对话框

P1 — 题库管理增强:
- QuestionBankItem 新增 tags 字段（多标签过滤）
- 新增 question_bank_templates 联表（题库跨模板复用）

P2 — 考试配置增强:
- AssessmentTemplate 新增字段:
  - attemptLimit (尝试次数限制)
  - scheduledStart/scheduledEnd (预约时段)
  - reviewMode (回顾模式: none/after_completion/per_question)
  - shuffleQuestions (每题随机排序)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/assessment/entities/question-bank-template.entity.ts

@@ -0,0 +1,37 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  ManyToOne,
+  JoinColumn,
+} from 'typeorm';
+import { QuestionBank } from './question-bank.entity';
+import { AssessmentTemplate } from './assessment-template.entity';
+
+/**
+ * P1: Join table for QuestionBank <-> AssessmentTemplate many-to-many
+ * Allows one question bank to be used across multiple templates.
+ */
+@Entity('question_bank_templates')
+export class QuestionBankTemplate {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ name: 'bank_id' })
+  bankId: string;
+
+  @ManyToOne(() => QuestionBank, (bank) => bank.id, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'bank_id' })
+  bank: QuestionBank;
+
+  @Column({ name: 'template_id' })
+  templateId: string;
+
+  @ManyToOne(() => AssessmentTemplate, (tpl) => tpl.id, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'template_id' })
+  template: AssessmentTemplate;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+}