feat(teacher): 题库模块（QuestionBank）

工作内容

- 新增 /teacher/questions 页面，支持 Suspense/空状态/加载态

- 题库 CRUD Server Actions：创建/更新/递归删除子题，变更后 revalidatePath

- getQuestions 支持 q/type/difficulty/knowledgePointId 筛选与分页返回 meta

- UI：表格列/筛选器/创建编辑弹窗，content JSON 兼容组卷

- 更新中文设计文档：docs/design/004_question_bank_implementation.md

src/modules/questions/data-access.ts

@@ -2,41 +2,52 @@ import 'server-only';
 
 import { db } from "@/shared/db";
 import { questions, questionsToKnowledgePoints } from "@/shared/db/schema";
-import { and, eq, inArray, count, desc, sql } from "drizzle-orm";
+import { and, count, desc, eq, inArray, sql, type SQL } from "drizzle-orm";
 import { cache } from "react";
+import type { Question, QuestionType } from "./types";
 
-// Types for filters
 export type GetQuestionsParams = {
+  q?: string;
   page?: number;
   pageSize?: number;
   ids?: string[];
   knowledgePointId?: string;
+  type?: QuestionType;
   difficulty?: number;
 };
 
-// Cached Data Access Function
-// Using React's cache() to deduplicate requests if called multiple times in one render pass
 export const getQuestions = cache(async ({
+  q,
   page = 1,
-  pageSize = 10,
+  pageSize = 50,
   ids,
   knowledgePointId,
+  type,
   difficulty,
 }: GetQuestionsParams = {}) => {
   const offset = (page - 1) * pageSize;
 
-  // Build Where Conditions
-  const conditions = [];
+  const conditions: SQL[] = [];
 
   if (ids && ids.length > 0) {
     conditions.push(inArray(questions.id, ids));
   }
 
+  if (q && q.trim().length > 0) {
+    const needle = `%${q.trim().toLowerCase()}%`;
+    conditions.push(
+      sql`LOWER(CAST(${questions.content} AS CHAR)) LIKE ${needle}`
+    );
+  }
+
+  if (type) {
+    conditions.push(eq(questions.type, type));
+  }
+
   if (difficulty) {
     conditions.push(eq(questions.difficulty, difficulty));
   }
 
-  // Filter by Knowledge Point (using subquery pattern for Many-to-Many)
   if (knowledgePointId) {
     const subQuery = db
       .select({ questionId: questionsToKnowledgePoints.questionId })
@@ -52,29 +63,24 @@ export const getQuestions = cache(async ({
 
   const whereClause = conditions.length > 0 ? and(...conditions) : undefined;
 
-  // 1. Get Total Count (for Pagination)
-  // Optimization: separate count query is often faster than fetching all data
   const [totalResult] = await db
     .select({ count: count() })
     .from(questions)
     .where(whereClause);
   
-  const total = totalResult?.count ?? 0;
+  const total = Number(totalResult?.count ?? 0);
 
-  // 2. Get Data with Relations
-  const data = await db.query.questions.findMany({
+  const rows = await db.query.questions.findMany({
     where: whereClause,
     limit: pageSize,
     offset: offset,
     orderBy: [desc(questions.createdAt)],
     with: {
-      // Preload Knowledge Points
       questionsToKnowledgePoints: {
         with: {
           knowledgePoint: true,
         },
       },
-      // Preload Author
       author: {
         columns: {
           id: true,
@@ -82,13 +88,37 @@ export const getQuestions = cache(async ({
           image: true,
         },
       },
-      // Preload Child Questions (first level)
       children: true, 
     },
   });
 
   return {
-    data,
+    data: rows.map((row) => {
+      const knowledgePoints =
+        row.questionsToKnowledgePoints?.map((rel) => rel.knowledgePoint) ?? [];
+
+      const author = row.author
+        ? {
+            id: row.author.id,
+            name: row.author.name,
+            image: row.author.image,
+          }
+        : null;
+
+      const mapped: Question = {
+        id: row.id,
+        content: row.content,
+        type: row.type,
+        difficulty: row.difficulty ?? 1,
+        createdAt: row.createdAt,
+        updatedAt: row.updatedAt,
+        author,
+        knowledgePoints: knowledgePoints.map((kp) => ({ id: kp.id, name: kp.name })),
+        childrenCount: row.children?.length ?? 0,
+      };
+
+      return mapped;
+    }),
     meta: {
       page,
       pageSize,