fix: golangci-lint 零告警通过 (57→0) + gofumpt/goimports 全量格式化

## CI 修复 (P0/P1)

P0 — 编译阻塞:
  - interfaces.go: postUseCase ISP 接口移除不用的 Create/Update/Delete

P1 — 必须修复:
  - ST1000: 为 13 个包添加包注释 (common/config/model/service/...)
  - ST1005: redis_store.go 全部错误消息改为小写开头
  - errcheck (19处): defer Close()→闭包忽略, notifier.Create→_=, r.Run→检查error
  - errorlint (9处): switch-on-error→errors.Is 链, ==→errors.Is
  - ST1020/ST1022: 导出符号注释以符号名开头

P2 — 安全评审:
  - gosec (12处): G203/G301/G304/G306 添加 nolint 注释并附理由

P3 — 清理:
  - unused: 移除 hasUnicode/energyStore/current/energyAdminUseCase
  - gofumpt + goimports 全量格式化 (35+ 文件)

internal/controller/admin/admin_controller.go

@@ -1,6 +1,8 @@
+// Package admin 提供管理后台的 HTTP 控制器：用户管理、审核、站点设置等。
 package admin
 
 import (
+	"errors"
 	"net/http"
 	"strconv"
 
@@ -104,9 +106,10 @@ func (ac *AdminController) UpdateUserStatus(c *gin.Context) {
 	}
 
 	action := "封禁"
-	if req.Status == model.StatusActive {
+	switch req.Status {
+	case model.StatusActive:
 		action = "解封"
-	} else if req.Status == model.StatusLocked {
+	case model.StatusLocked:
 		action = "已锁定"
 	}
 	common.OkMessage(c, action+"成功")
@@ -140,14 +143,13 @@ func parseUIDParam(c *gin.Context) (uint, error) {
 
 // handleServiceError 统一处理 service 层返回的错误
 func handleServiceError(c *gin.Context, err error) {
-	switch err {
-	case common.ErrPermissionDenied:
+	if errors.Is(err, common.ErrPermissionDenied) {
 		common.Error(c, http.StatusForbidden, "权限不足")
-	case common.ErrUserNotFound:
+	} else if errors.Is(err, common.ErrUserNotFound) {
 		common.Error(c, http.StatusNotFound, "用户不存在")
-	case common.ErrEmailExists:
+	} else if errors.Is(err, common.ErrEmailExists) {
 		common.Error(c, http.StatusConflict, "该邮箱已被其他用户注册，无法解锁")
-	default:
+	} else {
 		common.Error(c, http.StatusInternalServerError, "操作失败")
 	}
 }

internal/controller/admin/admin_energy_api_controller.go

@@ -1,6 +1,7 @@
 package admin
 
 import (
+	"errors"
 	"net/http"
 	"strconv"
 
@@ -44,7 +45,7 @@ func (ac *AdminEnergyController) AdjustEnergy(c *gin.Context) {
 	}
 
 	if err := ac.energySvc.AdminAdjust(operatorUID.(uint), req.UserIDs, req.Amount, req.Description, req.Mode); err != nil {
-		if err == common.ErrInsufficientFund {
+		if errors.Is(err, common.ErrInsufficientFund) {
 			common.Error(c, http.StatusBadRequest, "公户余额不足，无法执行操作")
 			return
 		}
@@ -99,7 +100,7 @@ func (ac *AdminEnergyController) GetFundBalance(c *gin.Context) {
 		return
 	}
 	common.Ok(c, gin.H{
-		"balance":        balance,
+		"balance":         balance,
 		"balance_display": float64(balance) / 10,
 	})
 }

internal/controller/admin/audit_controller.go

@@ -1,6 +1,7 @@
 package admin
 
 import (
+	"errors"
 	"net/http"
 	"strconv"
 
@@ -125,16 +126,15 @@ func parseIDParam(s string) (uint, error) {
 
 // handleAuditError 统一处理审核接口的 service 层错误
 func handleAuditError(c *gin.Context, err error) {
-	switch err {
-	case common.ErrAuditNotFound:
+	if errors.Is(err, common.ErrAuditNotFound) {
 		common.Error(c, http.StatusNotFound, "审核记录不存在")
-	case common.ErrAuditNotPending:
+	} else if errors.Is(err, common.ErrAuditNotPending) {
 		common.Error(c, http.StatusBadRequest, "该审核记录已处理")
-	case common.ErrUserNotFound:
+	} else if errors.Is(err, common.ErrUserNotFound) {
 		common.Error(c, http.StatusNotFound, "用户不存在")
-	case common.ErrUsernameTaken:
+	} else if errors.Is(err, common.ErrUsernameTaken) {
 		common.Error(c, http.StatusConflict, "该用户名已被其他用户占用，审批失败")
-	default:
+	} else {
 		common.Error(c, http.StatusInternalServerError, "操作失败")
 	}
 }

internal/controller/admin/site_setting_controller.go

@@ -24,7 +24,7 @@ func NewSiteSettingController(settingService siteSettingUseCase, defaults *servi
 // SiteSettingsPage 站点设置管理页面
 func (sc *SiteSettingController) SiteSettingsPage(c *gin.Context) {
 	c.HTML(http.StatusOK, "admin/site-settings/index.html", common.BuildAdminPageData(c, gin.H{
-		"Title":   "站点设置",
+		"Title":    "站点设置",
 		"ExtraCSS": "/admin/static/css/site-settings.css",
 		"ExtraJS":  "/admin/static/js/site-settings.js",
 	}))