feat: 新增备课模块并修复全模块 P0/P1/P2 缺陷

主要变更:

- 新增 lesson-preparation 模块: 备课编辑器、节点编辑、AI 建议、知识点选择、版本历史、作业发布

- 新增 shared 通用组件: charts/question-bank-filters/schedule-list/ui (chip-nav/filter-bar/page-header/stat-card/stat-item)

- 新增 student/admin 端 loading.tsx 与 error.tsx, 优化加载与错误态体验

- 新增 teacher/lesson-plans 页面 (列表/新建/编辑)

- 新增 drizzle 迁移 0002_tiny_lionheart 及 snapshot

- 新增 textbooks/schema.ts 与 exams/utils/normalize-structure.ts

- 修复 Tiptap v3 SSR hydration 崩溃 (rich-text-block immediatelyRender: false)

- 重构多模块 data-access/actions/组件, 修复权限校验与类型规范

- 同步架构文档 004/005 反映新增模块、导出、依赖关系

- 归档 bugs/* 测试报告与 e2e 测试脚本 (admin/parent/student/teacher web_test)

src/app/(dashboard)/teacher/homework/assignments/page.tsx

@@ -1,3 +1,4 @@
+import type { JSX } from "react"
 import Link from "next/link"
 import { EmptyState } from "@/shared/components/ui/empty-state"
 import { Badge } from "@/shared/components/ui/badge"
@@ -11,6 +12,7 @@ import {
   TableRow,
 } from "@/shared/components/ui/table"
 import { formatDate } from "@/shared/lib/utils"
+import { getParam, type SearchParams } from "@/shared/lib/search-params"
 import { getHomeworkAssignments } from "@/modules/homework/data-access"
 import { getTeacherClasses } from "@/modules/classes/data-access"
 import { PenTool, PlusCircle } from "lucide-react"
@@ -18,36 +20,33 @@ import { getTeacherIdForMutations } from "@/modules/classes/data-access"
 
 export const dynamic = "force-dynamic"
 
-type SearchParams = { [key: string]: string | string[] | undefined }
-
-const getParam = (params: SearchParams, key: string) => {
-  const v = params[key]
-  return Array.isArray(v) ? v[0] : v
-}
-
-export default async function AssignmentsPage({ searchParams }: { searchParams: Promise<SearchParams> }) {
+export default async function AssignmentsPage({ searchParams }: { searchParams: Promise<SearchParams> }): Promise<JSX.Element> {
   const sp = await searchParams
-  const classId = getParam(sp, "classId") || undefined
+  const rawClassId = getParam(sp, "classId")
   const creatorId = await getTeacherIdForMutations()
 
+  // Only fetch classes list when a class filter is active — needed to resolve
+  // the class name for display. When no filter is applied, skip the query to
+  // avoid an unnecessary DB round-trip.
+  const filteredClassId = rawClassId && rawClassId !== "all" ? rawClassId : null
   const [assignments, classes] = await Promise.all([
-    getHomeworkAssignments({ creatorId, classId: classId && classId !== "all" ? classId : undefined }),
-    classId && classId !== "all" ? getTeacherClasses() : Promise.resolve([]),
+    getHomeworkAssignments({ creatorId, classId: filteredClassId ?? undefined }),
+    filteredClassId ? getTeacherClasses() : Promise.resolve([]),
   ])
   const hasAssignments = assignments.length > 0
-  const className = classId && classId !== "all" ? classes.find((c) => c.id === classId)?.name : undefined
+  const className = filteredClassId ? classes.find((c) => c.id === filteredClassId)?.name : undefined
 
   return (
     <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
       <div className="flex items-center justify-between space-y-2">
         <div>
-          <h2 className="text-2xl font-bold tracking-tight">Assignments</h2>
+          <h1 className="text-2xl font-bold tracking-tight">Assignments</h1>
           <p className="text-muted-foreground">
-            {classId && classId !== "all" ? `Filtered by class: ${className ?? classId}` : "Manage homework assignments."}
+            {filteredClassId ? `Filtered by class: ${className ?? filteredClassId}` : "Manage homework assignments."}
           </p>
         </div>
         <div className="flex items-center gap-2">
-          {classId && classId !== "all" ? (
+          {filteredClassId ? (
             <Button asChild variant="outline">
               <Link href="/teacher/homework/assignments">Clear filter</Link>
             </Button>
@@ -55,12 +54,12 @@ export default async function AssignmentsPage({ searchParams }: { searchParams:
           <Button asChild>
             <Link
               href={
-                classId && classId !== "all"
-                  ? `/teacher/homework/assignments/create?classId=${encodeURIComponent(classId)}`
+                filteredClassId
+                  ? `/teacher/homework/assignments/create?classId=${encodeURIComponent(filteredClassId)}`
                   : "/teacher/homework/assignments/create"
               }
             >
-              <PlusCircle className="mr-2 h-4 w-4" />
+              <PlusCircle className="mr-2 h-4 w-4" aria-hidden="true" />
               Create Assignment
             </Link>
           </Button>
@@ -70,13 +69,13 @@ export default async function AssignmentsPage({ searchParams }: { searchParams:
       {!hasAssignments ? (
         <EmptyState
           title="No assignments"
-          description={classId && classId !== "all" ? "No assignments for this class yet." : "You haven't created any assignments yet."}
+          description={filteredClassId ? "No assignments for this class yet." : "You haven't created any assignments yet."}
           icon={PenTool}
           action={{
             label: "Create Assignment",
             href:
-              classId && classId !== "all"
-                ? `/teacher/homework/assignments/create?classId=${encodeURIComponent(classId)}`
+              filteredClassId
+                ? `/teacher/homework/assignments/create?classId=${encodeURIComponent(filteredClassId)}`
                 : "/teacher/homework/assignments/create",
           }}
         />
@@ -96,7 +95,10 @@ export default async function AssignmentsPage({ searchParams }: { searchParams:
               {assignments.map((a) => (
                 <TableRow key={a.id}>
                   <TableCell className="font-medium">
-                    <Link href={`/teacher/homework/assignments/${a.id}`} className="hover:underline">
+                    <Link
+                      href={`/teacher/homework/assignments/${a.id}`}
+                      className="hover:underline line-clamp-2 max-w-[240px]"
+                    >
                       {a.title}
                     </Link>
                   </TableCell>
@@ -105,9 +107,9 @@ export default async function AssignmentsPage({ searchParams }: { searchParams:
                       {a.status}
                     </Badge>
                   </TableCell>
-                  <TableCell>{a.dueAt ? formatDate(a.dueAt) : "-"}</TableCell>
-                  <TableCell className="text-muted-foreground">{a.sourceExamTitle}</TableCell>
-                  <TableCell className="text-muted-foreground">{formatDate(a.createdAt)}</TableCell>
+                  <TableCell className="text-muted-foreground tabular-nums">{a.dueAt ? formatDate(a.dueAt) : "-"}</TableCell>
+                  <TableCell className="text-muted-foreground truncate max-w-[200px]">{a.sourceExamTitle}</TableCell>
+                  <TableCell className="text-muted-foreground tabular-nums">{formatDate(a.createdAt)}</TableCell>
                 </TableRow>
               ))}
             </TableBody>