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/auth_controller.go

@@ -37,7 +37,7 @@ func (ac *AuthController) RegisterPage(c *gin.Context) {
 	guidelinesHTML := ac.siteSettings.Get("site.guidelines", "")
 	var guidelines template.HTML
 	if guidelinesHTML != "" {
-		guidelines = template.HTML(guidelinesHTML)
+		guidelines = template.HTML(guidelinesHTML) //nolint:gosec // 准则内容由管理员配置，属信任输入
 	} else {
 		content, err := theme.LoadContent("templates/MetaLab-2026/guidelines.html")
 		if err != nil {
@@ -48,10 +48,12 @@ func (ac *AuthController) RegisterPage(c *gin.Context) {
 	}
 	// 替换准则中的硬编码站点名和邮箱
 	siteInfo := ac.siteSettings.SiteInfo()
-	guidelines = template.HTML(strings.ReplaceAll(
-		strings.ReplaceAll(string(guidelines), "MetaLab", siteInfo.SiteName),
-		"metazone@foxmail.com", siteInfo.ContactEmail,
-	))
+	guidelines = template.HTML( //nolint:gosec // 准则内容由管理员配置，站点名/邮箱来自 DB
+		strings.ReplaceAll(
+			strings.ReplaceAll(string(guidelines), "MetaLab", siteInfo.SiteName),
+			"metazone@foxmail.com", siteInfo.ContactEmail,
+		),
+	)
 	c.HTML(http.StatusOK, "auth/register.html", common.BuildPageData(c, gin.H{
 		"Title":               "注册",
 		"ExtraCSS":            "/static/css/auth.css",