refactor: 后端仓库层更名为数据访问层（internal/repository → internal/dal）

「仓库层」是 repository 的直译，中文里与「代码仓库 / git 仓库」同词，
而这一层做的事就是数据访问。名字改成它实际在做的事。

改名口径（纯机械替换，无逻辑改动）：
- 包：internal/repository → internal/dal（package repository → package dal）
- 类型：XxxRepo → XxxDAO（TaskRecordDAO / SpecialistDAO / PositionDAO …）
- 变量：xxxRepo → xxxDAO
- import 路径、包限定符、日志前缀 [repository] → [dal] 同步
- 注释里的「仓库层」→「数据访问层」；core.go 包注释补上 DAL/DAO 全称

命名规范补登（AR09 是命名问题的最高依据，改了名就得回去登记）：
- AR09 §3.1 术语表新增「数据访问层 dal / DAO」一行
- AR09 §5.6 缩写表新增 DAO / dal —— 原文是「只有下表内的缩写允许使用」，
  不登记就是自己破自己的规矩
- PROJECT_STATE.md 新增 D27 记录本次更名决策

验证：全部在 db 副本上做，生产库 data/eai_agentplatform.db 未触碰。
- 等价性对照：拿 HEAD 源码 + 仅改名 造出第二棵树，两棵树各自起
  httptest 服务跑同一份探针（60 个 GET + 13 个写/回读，覆盖专员/技能/应用/
  任务/交付物/项目/岗位/考试/知识/积分/管理端只读等），逐端点比对响应体：
  73 项里 52 项字节完全一致、21 项仅运行期时间戳不同、内容差异 0。
- 探针非空：往改名后的树注入「SpecialistDAO.List 限 3 条」变异，
  /api/specialists 立刻被抓出 —— 证明上面那个 0 不是没测到。
- 暂存区自洽：把索引整个导出成源码树，go build / go vet / go test ./... 全绿。
- gofmt：因 import 排序变化而错位的 19 个文件已修；另 2 个文件（skill_definition.go、
  seed.go）的格式问题是工作区里别人的在制品带来的，未替其改动。

未纳入本次提交：工作区里正在进行中的「文生语音技能 + 技能展示色/交互卡」
（tts_handlers.go、text_to_speech/manifest.go、skillCatalog.js 等），
以及 router.go / skill_definition.go / seed.go 三个文件里属于该在制品的改动 ——
这三个文件只把「改名那一版」放进索引，工作区原样保留。

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

eai_agentplatform/backend-go/internal/api/exam.go

@@ -14,25 +14,25 @@ import (
 	"github.com/golang-jwt/jwt/v5"
 
 	"eai_agentplatform/backend/internal/auth"
+	"eai_agentplatform/backend/internal/dal"
 	"eai_agentplatform/backend/internal/middleware"
 	"eai_agentplatform/backend/internal/model"
-	"eai_agentplatform/backend/internal/repository"
 	"eai_agentplatform/backend/internal/web"
 )
 
 // 考试域仓库，包内共享（知识源摄入也会写题目，见 knowledge.go）。
 var (
-	mistakeRepo    repository.MistakeRecordRepo
-	questionRepo   repository.QuestionRepo
-	paperRepo      repository.ExamPaperRepo
-	examRecordRepo repository.ExamRecordRepo
+	mistakeDAO    dal.MistakeRecordDAO
+	questionDAO   dal.QuestionDAO
+	paperDAO      dal.ExamPaperDAO
+	examRecordDAO dal.ExamRecordDAO
 )
 
 func init() {
-	mistakeRepo = repository.MistakeRecordRepo{}
-	questionRepo = repository.QuestionRepo{}
-	paperRepo = repository.ExamPaperRepo{}
-	examRecordRepo = repository.ExamRecordRepo{}
+	mistakeDAO = dal.MistakeRecordDAO{}
+	questionDAO = dal.QuestionDAO{}
+	paperDAO = dal.ExamPaperDAO{}
+	examRecordDAO = dal.ExamRecordDAO{}
 }
 
 // Option 题目选项
@@ -84,7 +84,7 @@ func questionView(q model.Question) gin.H {
 // ListQuestions GET /api/exam/questions?domain=&status=
 func ListQuestions(c *gin.Context) {
 	// 管理端题库：status 缺省要看到全部（含已停用），按约定传 "all"
-	items := questionRepo.List(c.Query("domain"), orDefault(c.Query("status"), "all"))
+	items := questionDAO.List(c.Query("domain"), orDefault(c.Query("status"), "all"))
 	out := make([]gin.H, 0, len(items))
 	for _, it := range items {
 		out = append(out, questionView(it))
@@ -119,7 +119,7 @@ func CreateQuestion(c *gin.Context) {
 		Explanation: req.Explanation,
 		Status:      "active",
 	}
-	if !questionRepo.Insert(&q) {
+	if !questionDAO.Insert(&q) {
 		web.Fail(c, web.NewBadRequest("创建题目失败"))
 		return
 	}
@@ -132,7 +132,7 @@ func UpdateQuestion(c *gin.Context) {
 	if !ok {
 		return
 	}
-	q, found := questionRepo.GetByID(id)
+	q, found := questionDAO.GetByID(id)
 	if !found {
 		web.Fail(c, web.NewNotFoundError("题目不存在"))
 		return
@@ -159,7 +159,7 @@ func UpdateQuestion(c *gin.Context) {
 	q.Options = string(optsJSON)
 	q.Answer = string(ansJSON)
 	q.Explanation = req.Explanation
-	if !questionRepo.Update(&q) {
+	if !questionDAO.Update(&q) {
 		web.Fail(c, web.NewBadRequest("更新题目失败"))
 		return
 	}
@@ -172,11 +172,11 @@ func DeleteQuestion(c *gin.Context) {
 	if !ok {
 		return
 	}
-	if _, found := questionRepo.GetByID(id); !found {
+	if _, found := questionDAO.GetByID(id); !found {
 		web.Fail(c, web.NewNotFoundError("题目不存在"))
 		return
 	}
-	if !questionRepo.Delete(id) {
+	if !questionDAO.Delete(id) {
 		web.Fail(c, web.NewBadRequest("停用题目失败"))
 		return
 	}
@@ -187,7 +187,7 @@ func DeleteQuestion(c *gin.Context) {
 
 // ListPapers GET /api/exam/papers
 func ListPapers(c *gin.Context) {
-	web.OK(c, paperRepo.List())
+	web.OK(c, paperDAO.List())
 }
 
 // CreatePaper POST /api/exam/papers (admin)
@@ -208,7 +208,7 @@ func CreatePaper(c *gin.Context) {
 		return
 	}
 	p.Status = "active"
-	if !paperRepo.Insert(&p) {
+	if !paperDAO.Insert(&p) {
 		web.Fail(c, web.NewBadRequest("创建考试失败"))
 		return
 	}
@@ -221,7 +221,7 @@ func UpdatePaper(c *gin.Context) {
 	if !ok {
 		return
 	}
-	p, found := paperRepo.GetByID(id)
+	p, found := paperDAO.GetByID(id)
 	if !found {
 		web.Fail(c, web.NewNotFoundError("考试配置不存在"))
 		return
@@ -253,7 +253,7 @@ func UpdatePaper(c *gin.Context) {
 	if req.Status != "" {
 		p.Status = req.Status
 	}
-	if !paperRepo.Update(&p) {
+	if !paperDAO.Update(&p) {
 		web.Fail(c, web.NewBadRequest("更新考试失败"))
 		return
 	}
@@ -266,11 +266,11 @@ func DeletePaper(c *gin.Context) {
 	if !ok {
 		return
 	}
-	if _, found := paperRepo.GetByID(id); !found {
+	if _, found := paperDAO.GetByID(id); !found {
 		web.Fail(c, web.NewNotFoundError("考试配置不存在"))
 		return
 	}
-	if !paperRepo.Delete(id) {
+	if !paperDAO.Delete(id) {
 		web.Fail(c, web.NewBadRequest("停用考试失败"))
 		return
 	}
@@ -282,7 +282,7 @@ func DeletePaper(c *gin.Context) {
 // ExamList GET /api/exam/list —— 我的考试列表（含完成状态）
 func ExamList(c *gin.Context) {
 	u := middleware.CurrentUser(c)
-	items := paperRepo.GetActive()
+	items := paperDAO.GetActive()
 
 	type row struct {
 		ID              uint   `json:"id"`
@@ -298,7 +298,7 @@ func ExamList(c *gin.Context) {
 	out := make([]row, 0, len(items))
 	for _, p := range items {
 		st := "available"
-		if p.Type == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
+		if p.Type == "formal" && u != nil && examRecordDAO.HasTaken(u.ID, p.ID) {
 			st = "completed"
 		}
 		out = append(out, row{
@@ -318,7 +318,7 @@ func ExamCover(c *gin.Context) {
 		return
 	}
 	id := uint(id64)
-	p, found := paperRepo.GetByID(id)
+	p, found := paperDAO.GetByID(id)
 	if !found || p.Status != "active" {
 		web.Fail(c, web.NewNotFoundError("考试不存在或已停用"))
 		return
@@ -351,18 +351,18 @@ func pickQuestions(p model.ExamPaper) ([]model.Question, error) {
 	var courseIDs []uint
 	if p.PositionID != nil {
 		// 岗位考试：优先蓝图，其次岗位知识映射
-		if bps := positionRepo.Blueprints(*p.PositionID); len(bps) > 0 {
+		if bps := positionDAO.Blueprints(*p.PositionID); len(bps) > 0 {
 			return pickQuestionsByBlueprint(p, bps)
 		}
 		// 岗位考试：圈定岗位应学范围
-		domains, courseIDs = positionScope(positionRepo.Knowledge(*p.PositionID))
+		domains, courseIDs = positionScope(positionDAO.Knowledge(*p.PositionID))
 	} else {
 		// 原有逻辑：按 exam_paper.domain 抽题
 		domains = splitDomains(p.Domain)
 	}
 
 	var qs []model.Question
-	if !questionRepo.ActivePool(domains, courseIDs).Order("id ASC").Find(&qs) {
+	if !questionDAO.ActivePool(domains, courseIDs).Order("id ASC").Find(&qs) {
 		return nil, fmt.Errorf("查询题库失败")
 	}
 	if len(qs) < p.QuestionCount {
@@ -377,8 +377,8 @@ func pickQuestions(p model.ExamPaper) ([]model.Question, error) {
 // pickQuestionsByBlueprint 按岗位考试蓝图逐条抽题：先在岗位应学范围内，再按 (domain, type) 细分抽样。
 func pickQuestionsByBlueprint(p model.ExamPaper, bps []model.PositionExamBlueprint) ([]model.Question, error) {
 	// 圈定岗位应学范围（与 P0 岗位知识映射抽题一致）
-	domains, courseIDs := positionScope(positionRepo.Knowledge(*p.PositionID))
-	base := questionRepo.ActivePool(domains, courseIDs)
+	domains, courseIDs := positionScope(positionDAO.Knowledge(*p.PositionID))
+	base := questionDAO.ActivePool(domains, courseIDs)
 
 	out := make([]model.Question, 0, p.QuestionCount)
 	used := map[uint]bool{}
@@ -456,12 +456,12 @@ func validatePaperPosition(c *gin.Context, positionID *uint) bool {
 	if positionID == nil {
 		return true
 	}
-	pos, found := positionRepo.GetByID(*positionID)
+	pos, found := positionDAO.GetByID(*positionID)
 	if !found || pos.Status != "active" {
 		web.Fail(c, web.NewBadRequest("关联岗位不存在或已停用"))
 		return false
 	}
-	if positionRepo.CountKnowledge(*positionID) == 0 {
+	if positionDAO.CountKnowledge(*positionID) == 0 {
 		web.Fail(c, web.NewBadRequest("岗位考试必须先配置岗位知识映射"))
 		return false
 	}
@@ -473,7 +473,7 @@ func validatePaperBlueprintCount(c *gin.Context, p model.ExamPaper) bool {
 	if p.PositionID == nil {
 		return true
 	}
-	bps := positionRepo.Blueprints(*p.PositionID)
+	bps := positionDAO.Blueprints(*p.PositionID)
 	if len(bps) == 0 {
 		return true
 	}
@@ -509,12 +509,12 @@ func ExamStart(c *gin.Context) {
 		web.Fail(c, web.NewBadRequest("paper_id 必填"))
 		return
 	}
-	p, found := paperRepo.GetByID(req.PaperID)
+	p, found := paperDAO.GetByID(req.PaperID)
 	if !found || p.Status != "active" {
 		web.Fail(c, web.NewNotFoundError("考试不存在或已停用"))
 		return
 	}
-	if p.Type == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
+	if p.Type == "formal" && u != nil && examRecordDAO.HasTaken(u.ID, p.ID) {
 		web.Fail(c, web.NewConflictError("已参加过该正式考试"))
 		return
 	}
@@ -676,7 +676,7 @@ func ExamSubmit(c *gin.Context) {
 			web.Fail(c, web.NewBadRequest("练习会话无题目"))
 			return
 		}
-		qs := questionRepo.ListByIDs(ids)
+		qs := questionDAO.ListByIDs(ids)
 		qmap := make(map[uint]model.Question, len(qs))
 		for _, q := range qs {
 			qmap[q.ID] = q
@@ -755,14 +755,14 @@ func ExamSubmit(c *gin.Context) {
 		return
 	}
 
-	p, found := paperRepo.GetByID(uint(pid))
+	p, found := paperDAO.GetByID(uint(pid))
 	if !found {
 		web.Fail(c, web.NewNotFoundError("考试不存在"))
 		return
 	}
 
 	// 正式考不可重复交卷
-	if stype == "formal" && u != nil && examRecordRepo.HasTaken(u.ID, p.ID) {
+	if stype == "formal" && u != nil && examRecordDAO.HasTaken(u.ID, p.ID) {
 		web.Fail(c, web.NewConflictError("已参加过该正式考试"))
 		return
 	}
@@ -772,7 +772,7 @@ func ExamSubmit(c *gin.Context) {
 		web.Fail(c, web.NewBadRequest("考试会话无题目"))
 		return
 	}
-	questions := questionRepo.ListByIDs(ids)
+	questions := questionDAO.ListByIDs(ids)
 	qmap := make(map[uint]model.Question, len(questions))
 	for _, q := range questions {
 		qmap[q.ID] = q
@@ -867,7 +867,7 @@ func ExamSubmit(c *gin.Context) {
 			CorrectCount: correctCount, WrongCount: wrongCount,
 			DetailJSON: string(detailJSON), SubmittedAt: time.Now(),
 		}
-		examRecordRepo.Insert(&rec)
+		examRecordDAO.Insert(&rec)
 		if passed {
 			awardPoints(u.ID, "formal_pass", ptFormalPass, "paper", p.ID)
 			issueCertificate(u, rec)
@@ -897,7 +897,7 @@ func splitIDs(s string) []uint {
 // ExamRecordList GET /api/exam/record?page=&size= —— 我的考试记录
 func ExamRecordList(c *gin.Context) {
 	u := middleware.CurrentUser(c)
-	items := examRecordRepo.ListByUser(u.ID)
+	items := examRecordDAO.ListByUser(u.ID)
 	if items == nil {
 		items = []model.ExamRecord{}
 	}
@@ -911,7 +911,7 @@ func ExamRecordDetail(c *gin.Context) {
 	if !ok {
 		return
 	}
-	rec, found := examRecordRepo.GetByID(id)
+	rec, found := examRecordDAO.GetByID(id)
 	if !found {
 		web.Fail(c, web.NewNotFoundError("考试记录不存在"))
 		return
@@ -947,7 +947,7 @@ func mistakePayload(userID, questionID uint, source string, q model.Question, us
 
 // recordMistake 答错入本：按 (user_id, question_id, source) 去重，再次答错则更新并重置为未掌握。
 func recordMistake(userID, questionID uint, q model.Question, userAns any, correct []string, source string) {
-	mistakeRepo.RecordWrong(mistakePayload(userID, questionID, source, q, userAns, correct))
+	mistakeDAO.RecordWrong(mistakePayload(userID, questionID, source, q, userAns, correct))
 }
 
 // mistakeView 错题出参（answer 反序列化，便于前端直接展示）
@@ -967,7 +967,7 @@ type mistakeView struct {
 // MyMistakes GET /api/exam/mistakes —— 我的错题本
 func MyMistakes(c *gin.Context) {
 	u := middleware.CurrentUser(c)
-	items := mistakeRepo.ListByUser(u.ID)
+	items := mistakeDAO.ListByUser(u.ID)
 	out := make([]mistakeView, 0, len(items))
 	for _, it := range items {
 		var userAns any
@@ -994,7 +994,7 @@ func ResolveMistake(c *gin.Context) {
 	if !ok {
 		return
 	}
-	rec, found := mistakeRepo.GetByID(id)
+	rec, found := mistakeDAO.GetByID(id)
 	if !found {
 		web.Fail(c, web.NewNotFoundError("错题记录不存在"))
 		return
@@ -1013,7 +1013,7 @@ func ResolveMistake(c *gin.Context) {
 	}
 	wasResolved := rec.Resolved
 	rec.Resolved = target
-	if !mistakeRepo.Update(&rec) {
+	if !mistakeDAO.Update(&rec) {
 		web.Fail(c, web.NewBadRequest("更新错题状态失败"))
 		return
 	}
@@ -1037,7 +1037,7 @@ func MistakePractice(c *gin.Context) {
 	}
 	_ = c.ShouldBindJSON(&req)
 
-	recs := mistakeRepo.ListForPractice(u.ID, req.Source, req.OnlyUnresolved)
+	recs := mistakeDAO.ListForPractice(u.ID, req.Source, req.OnlyUnresolved)
 	if len(recs) == 0 {
 		web.Fail(c, web.NewBadRequest("暂无可重练的错题"))
 		return
@@ -1050,7 +1050,7 @@ func MistakePractice(c *gin.Context) {
 	ids = dedupeUints(ids)
 
 	// 剔除已停用/删除的题目，仅下发可作答题目
-	questions := questionRepo.ListActiveByIDs(ids)
+	questions := questionDAO.ListActiveByIDs(ids)
 	if len(questions) == 0 {
 		web.Fail(c, web.NewBadRequest("错题对应题目已失效，暂无可重练题目"))
 		return
@@ -1101,11 +1101,11 @@ func MistakePractice(c *gin.Context) {
 // touchMistakeOnPractice 错题重练判分后同步错题状态：答对置为已掌握（加积分），答错重置为未掌握。
 func touchMistakeOnPractice(userID, questionID uint, q model.Question, userAns any, correct []string, resolved bool) {
 	payload := mistakePayload(userID, questionID, "", q, userAns, correct)
-	flipped, touched := mistakeRepo.TouchOnPractice(payload, resolved)
+	flipped, touched := mistakeDAO.TouchOnPractice(payload, resolved)
 	if !touched {
 		// 防御性兜底：理论上重练题目均来自错题本，这里创建一条
 		payload.Source = "re_practice"
-		mistakeRepo.RecordWrong(payload)
+		mistakeDAO.RecordWrong(payload)
 		return
 	}
 	// 仅在「未掌握 → 已掌握」时加分，避免反复重练刷分