refactor(lesson-preparation): V2 审计深度修复 — Server Actions i18n + 错误码模式 + 类型断言清零 + a11y 深度修复 + Tracker 埋点接入

V2-1: 12 个 Server Action 通过 getTranslations 翻译错误消息；Service/DataAccess 层抛出错误码异常（PublishServiceError/LessonPlanDataError），Actions 层通过 PUBLISH_ERROR_KEY_MAP 翻译为 i18n 消息
V2-2: SYSTEM_TEMPLATES name/title 改为 i18n 键，createLessonPlan 接受 translateTitle 函数在服务端翻译后存储到 DB
V2-3: 8 处 as unknown as 断言替换为显式类型映射函数（mapRowToLessonPlan/mapRowToListItem/mapRowToTemplate/mapRowToVersion）+ 类型守卫（isLessonPlanStatus/isTemplateType/isTemplateScope）
V2-4: MiniMap nodeColor 复用 lib/node-summary.ts 的 getNodeColor
V2-5: a11y 深度修复 — lesson-plan-filters/exercise-block/inline-question-editor 的 select 添加 label htmlFor 关联；exercise-block 题目列表改为 ul/li；node-editor 画布添加 role=application + 键盘导航配置
V2-6: Tracker 埋点接入 — 新增 useLessonPlanTrackerSafe hook，在 create/save/publish/revert/duplicate/archive 6 处调用 tracker.track

同步更新架构图 004 和 005 文档

src/modules/lesson-preparation/components/blocks/exercise-block.tsx

@@ -52,8 +52,12 @@ export function ExerciseBlock({ blockId, data, classes, textbookId, chapterId }:
 
   return (
     <div className="space-y-2">
-      <div className="flex gap-2">
+      <div className="flex gap-2 items-center">
+        <label htmlFor={`exercise-purpose-${blockId}`} className="text-sm font-medium">
+          {t("exercise.purposeLabel")}
+        </label>
         <select
+          id={`exercise-purpose-${blockId}`}
           value={data.purpose}
           onChange={(e) =>
             update({ purpose: e.target.value as ExercisePurpose })
@@ -69,9 +73,9 @@ export function ExerciseBlock({ blockId, data, classes, textbookId, chapterId }:
           {t("questionBank.empty")}
         </p>
       ) : (
-        <div className="space-y-1">
+        <ul className="space-y-1 list-none p-0" role="list">
           {data.items.map((item, idx) => (
-            <div
+            <li
               key={item.questionId}
               className="flex items-center gap-2 border rounded p-2"
             >
@@ -87,9 +91,9 @@ export function ExerciseBlock({ blockId, data, classes, textbookId, chapterId }:
               <button onClick={() => removeItem(idx)} aria-label={t("action.delete")}>
                 <Trash2 className="w-3 h-3 text-error" aria-hidden="true" />
               </button>
-            </div>
+            </li>
           ))}
-        </div>
+        </ul>
       )}
       <div className="flex gap-2 flex-wrap">
         <Button