refactor: cleanup unused code and simplify internal packages

This commit performs a significant cleanup of the codebase by removing unused functions, methods, and entire files across various internal modules. This reduces technical debt and simplifies the project structure.

Key changes include:
- **cache**: Removed unused cache key generators and metrics snapshots.
- **dto**: Removed redundant converter functions and segment creation helpers.
- **middleware**: Deleted the unused `logger.go` middleware and simplified `ratelimit.go` and `casbin.go`.
- **model**: Removed unused ID helpers, database closing functions, and batch decryption logic.
- **pkg**: Cleaned up unused utility functions in `circuitbreaker`, `crypto`, `cursor`, `hook`, and `utils`.
- **service**: Deleted `account_cleanup_service.go` and removed unused helper functions in `log_cleanup_service.go` and `sensitive_service.go`.
- **repository**: Removed unused private loading methods in `comment_repo.go`.

internal/pkg/cursor/builder.go

@@ -64,19 +64,6 @@ func (b *CursorBuilder) WithPageSize(size int) *CursorBuilder {
 	return b
 }
 
-// WithDirection 设置分页方向
-func (b *CursorBuilder) WithDirection(direction Direction) *CursorBuilder {
-	if b.err != nil {
-		return b
-	}
-
-	if direction == "" {
-		b.direction = Forward
-	} else {
-		b.direction = direction
-	}
-	return b
-}
 
 // Error 返回构建过程中的错误
 func (b *CursorBuilder) Error() error {
@@ -166,79 +153,11 @@ func HasMore(itemsLen int, pageSize int) bool {
 	return itemsLen > pageSize
 }
 
-// TrimItems 裁剪结果到实际页面大小
-func TrimItems(itemsLen int, pageSize int) int {
-	if itemsLen > pageSize {
-		return pageSize
-	}
-	return itemsLen
-}
 
-// BuildResponse 从结果构建响应
-// items: 结果切片（需要是切片类型）
-// getSortValue: 获取排序字段值的函数
-// getID: 获取ID的函数
-func BuildResponse[T any](items []T, order SortOrder, pageSize int, getSortValue func(T) string, getID func(T) string) *PageResponse {
-	hasMore := len(items) > pageSize
 
-	// 裁剪到实际页面大小
-	if hasMore {
-		items = items[:pageSize]
-	}
-
-	var nextCursor, prevCursor string
-
-	// 生成下一页游标
-	if hasMore && len(items) > 0 {
-		lastItem := items[len(items)-1]
-		nextCursor = NewCursor(getSortValue(lastItem), getID(lastItem), order).Encode()
-	}
-
-	return &PageResponse{
-		Items:      items,
-		NextCursor: nextCursor,
-		PrevCursor: prevCursor,
-		HasMore:    hasMore,
-	}
-}
-
-// BuildResponseWithPrev 从结果构建响应（包含上一页游标）
-func BuildResponseWithPrev[T any](items []T, order SortOrder, pageSize int, getSortValue func(T) string, getID func(T) string) *PageResponse {
-	hasMore := len(items) > pageSize
-
-	// 裁剪到实际页面大小
-	if hasMore {
-		items = items[:pageSize]
-	}
-
-	var nextCursor, prevCursor string
-
-	// 生成下一页游标
-	if hasMore && len(items) > 0 {
-		lastItem := items[len(items)-1]
-		nextCursor = NewCursor(getSortValue(lastItem), getID(lastItem), order).Encode()
-	}
-
-	// 生成上一页游标
-	if len(items) > 0 {
-		firstItem := items[0]
-		prevCursor = NewCursor(getSortValue(firstItem), getID(firstItem), order).Encode()
-	}
-
-	return &PageResponse{
-		Items:      items,
-		NextCursor: nextCursor,
-		PrevCursor: prevCursor,
-		HasMore:    hasMore,
-	}
-}
 
 // FormatTime 格式化时间为字符串（用于游标）
 func FormatTime(t time.Time) string {
 	return t.Format(time.RFC3339Nano)
 }
 
-// ParseTime 解析时间字符串（从游标）
-func ParseTime(s string) (time.Time, error) {
-	return time.Parse(time.RFC3339Nano, s)
-}

internal/pkg/cursor/pagination.go

@@ -99,15 +99,6 @@ type PageResponse struct {
 	HasMore    bool   `json:"has_more"`
 }
 
-// NewPageResponse 创建分页响应
-func NewPageResponse(items any, nextCursor, prevCursor string, hasMore bool) *PageResponse {
-	return &PageResponse{
-		Items:      items,
-		NextCursor: nextCursor,
-		PrevCursor: prevCursor,
-		HasMore:    hasMore,
-	}
-}
 
 // CursorPageResult 游标分页结果（泛型版本，供内部使用）
 type CursorPageResult[T any] struct {