chore: 清理 SSR 改造后的历史遗留死代码与误提交产物

- 删除图形验证码整条死链：service/captcha.go、APICaptcha、
  GET /api/captcha、CaptchaService 装配、ErrCaptchaInvalid 及前端
  api.captcha()（注册/登录已改用邮箱验证码，Verify 无任何调用方）
- 删除 GET /api/posts/hot 死路由：APIHotPosts + PostService.HotPosts
  （热门排序走 /api/posts?sort=hot）
- 删除 GET /api/posts/:id/revisions/:revId 死路由：
  APIPostRevisionDetail + PostService.GetRevision + ErrRevisionNotFound
  及前端 api.postRevision()（历史面板仅用列表接口）
- 停止跟踪误提交的 27.5MB Linux 二进制 jiang13-linux-amd64 与
  .vite 依赖缓存；.gitignore 补充对应规则并移除已失效的
  embed_static 条目

service/post.go

@@ -172,52 +172,6 @@ func (s *PostService) lastReplyInfoMap(postIDs []uint) map[uint]lastReplyInfo {
 	return m
 }
 
-// HotPosts 近期活跃讨论（近 7 日有公开回复，按最后回复时间倒序）
-func (s *PostService) HotPosts(limit int) ([]PostListItem, error) {
-	if limit <= 0 {
-		limit = 10
-	}
-	since := time.Now().Add(-7 * 24 * time.Hour)
-	var posts []model.Post
-	err := model.DB.Preload("User").Preload("Board").
-		Where("status = ?", model.ContentStatusPublished).
-		Where(`EXISTS (
-			SELECT 1 FROM comments
-			WHERE comments.post_id = posts.id
-			AND comments.deleted_at IS NULL
-			AND comments.status = ?
-			AND comments.created_at >= ?
-		)`, model.ContentStatusPublished, since).
-		Order(`(
-			SELECT MAX(created_at) FROM comments
-			WHERE comments.post_id = posts.id
-			AND comments.deleted_at IS NULL
-			AND comments.status = 'published'
-		) DESC`).
-		Limit(limit).Find(&posts).Error
-	if err != nil {
-		return nil, err
-	}
-	ids := make([]uint, len(posts))
-	for i, p := range posts {
-		ids[i] = p.ID
-	}
-	countMap := s.commentCountMap(ids)
-	replyMap := s.lastReplyInfoMap(ids)
-	items := make([]PostListItem, len(posts))
-	for i, p := range posts {
-		info := replyMap[p.ID]
-		items[i] = PostListItem{
-			Post:               p,
-			CommentCount:       countMap[p.ID],
-			LastReplyAt:        info.At,
-			LastReplyUser:      info.User,
-			LastReplyGuestNick: info.GuestNick,
-		}
-	}
-	return items, nil
-}
-
 // TagCount 标签及其出现次数
 type TagCount struct {
 	Name  string `json:"name"`
@@ -680,16 +634,6 @@ func (s *PostService) ListRevisions(postID uint) ([]model.PostRevision, error) {
 	return revs, nil
 }
 
-func (s *PostService) GetRevision(postID, revID uint) (*model.PostRevision, error) {
-	var rev model.PostRevision
-	err := model.DB.Preload("Editor").
-		Where("id = ? AND post_id = ?", revID, postID).First(&rev).Error
-	if err != nil {
-		return nil, ErrRevisionNotFound
-	}
-	return &rev, nil
-}
-
 // Delete 软删除帖子及其评论（进入回收站）；点赞/收藏保留以便恢复。仅管理员可删。
 func (s *PostService) Delete(userID, postID uint, isAdmin bool) error {
 	if !isAdmin {