chore: 补充后端核心模块的中文注释

backend/internal/feed/repo.go

@@ -17,6 +17,7 @@ func NewFeedRepository(db *gorm.DB) *FeedRepository {
 	return &FeedRepository{db: db}
 }
 
+// 查询最新视频. limit: 查询数量  latestBefore: 查询早于此时间的视频(零值则不限制)
 func (repo *FeedRepository) ListLatest(ctx context.Context, limit int, latestBefore time.Time) ([]*video.Video, error) {
 	var videos []*video.Video
 	query := repo.db.WithContext(ctx).Model(&video.Video{}).
@@ -30,6 +31,7 @@ func (repo *FeedRepository) ListLatest(ctx context.Context, limit int, latestBef
 	return videos, nil
 }
 
+// 查询点赞数最多的视频. limit: 查询数量  cursor: 游标
 func (repo *FeedRepository) ListLikesCountWithCursor(ctx context.Context, limit int, cursor *LikesCountCursor) ([]*video.Video, error) {
 	var videos []*video.Video
 	query := repo.db.WithContext(ctx).Model(&video.Video{}).
@@ -49,6 +51,7 @@ func (repo *FeedRepository) ListLikesCountWithCursor(ctx context.Context, limit
 	return videos, nil
 }
 
+// 查询关注用户的视频. limit: 查询数量  viewerAccountID: 查看者账户ID  latestBefore: 查询早于此时间的视频(零值则不限制)
 func (repo *FeedRepository) ListByFollowing(ctx context.Context, limit int, viewerAccountID uint, latestBefore time.Time) ([]*video.Video, error) {
 	var videos []*video.Video
 	query := repo.db.WithContext(ctx).Model(&video.Video{}).
@@ -69,6 +72,7 @@ func (repo *FeedRepository) ListByFollowing(ctx context.Context, limit int, view
 	return videos, nil
 }
 
+// 查询热门视频. limit: 查询数量  popularityBefore: 查询热度低于此值的视频  timeBefore: 查询早于此时间的视频  idBefore: 查询ID小于此值的视频
 func (repo *FeedRepository) ListByPopularity(ctx context.Context, limit int, popularityBefore int64, timeBefore time.Time, idBefore uint) ([]*video.Video, error) {
 	var videos []*video.Video
 	query := repo.db.WithContext(ctx).Model(&video.Video{}).