refactor: 文件行数超标拆解（7个文件→14个文件，全部≤200行）

- 移动本地接口定义到 interfaces.go 和 admin/interfaces.go
- favorite_controller.go → favorite_item_controller.go
- space_controller.go → space_loaders.go
- settings_controller.go → settings_api_audit.go
- admin_energy_controller.go → admin_energy_api_controller.go
- admin_post_controller.go → admin_post_action_controller.go
- comment_repo.go → comment_mention_repo.go
- post_repo.go → post_stats_repo.go

internal/controller/admin/interfaces.go

@@ -52,3 +52,11 @@ type adminCommentUseCase interface {
 	ListAllComments(keyword string, showDeleted bool, page, pageSize int) ([]model.AdminCommentRow, int64, error)
 	Delete(commentID uint, requesterID uint, isAdmin bool) error
 }
+
+// adminEnergyUseCase AdminEnergyController 对 EnergyService 的最小依赖（ISP：4 个方法）
+type adminEnergyUseCase interface {
+	AdminAdjust(operatorUID uint, userIDs []uint, amount int, description string, mode string) error
+	GetAdminEnergyLogs(energyType string, page, pageSize int) ([]model.EnergyLog, int64, error)
+	GetFundBalance() (int, error)
+	GetFundLogs(logType string, page, pageSize int) ([]model.FundLog, int64, error)
+}