feat: 品牌重命名 Sub2API -> TianShuAPI

- 前端: 所有界面显示、i18n 文本、组件中的品牌名称
- 后端: 服务层、设置默认值、邮件模板、安装向导
- 数据库: 迁移脚本注释
- 保持功能完全一致，仅更改品牌名称

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/server/middleware/admin_only.go

@@ -1,27 +1,27 @@
-package middleware
-
-import (
-	"github.com/Wei-Shaw/sub2api/internal/service"
-
-	"github.com/gin-gonic/gin"
-)
-
-// AdminOnly 管理员权限中间件
-// 必须在JWTAuth中间件之后使用
-func AdminOnly() gin.HandlerFunc {
-	return func(c *gin.Context) {
-		role, ok := GetUserRoleFromContext(c)
-		if !ok {
-			AbortWithError(c, 401, "UNAUTHORIZED", "User not found in context")
-			return
-		}
-
-		// 检查是否为管理员
-		if role != service.RoleAdmin {
-			AbortWithError(c, 403, "FORBIDDEN", "Admin access required")
-			return
-		}
-
-		c.Next()
-	}
-}
+package middleware
+
+import (
+	"github.com/Wei-Shaw/sub2api/internal/service"
+
+	"github.com/gin-gonic/gin"
+)
+
+// AdminOnly 管理员权限中间件
+// 必须在JWTAuth中间件之后使用
+func AdminOnly() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		role, ok := GetUserRoleFromContext(c)
+		if !ok {
+			AbortWithError(c, 401, "UNAUTHORIZED", "User not found in context")
+			return
+		}
+
+		// 检查是否为管理员
+		if role != service.RoleAdmin {
+			AbortWithError(c, 403, "FORBIDDEN", "Admin access required")
+			return
+		}
+
+		c.Next()
+	}
+}