feat(verification): add user identity verification system

Implement a complete user identity verification system with support for multiple identity types (student, teacher, staff, alumni). The system includes user-facing verification submission and status checking endpoints, admin endpoints for reviewing verification requests, middleware for protecting verification-required routes, and integration with the user model to track verification status.

internal/middleware/verification.go

@@ -0,0 +1,35 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+
+	"carrot_bbs/internal/model"
+	"carrot_bbs/internal/pkg/response"
+	"carrot_bbs/internal/repository"
+)
+
+func RequireVerification(userRepo repository.UserRepository) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID, exists := c.Get("user_id")
+		if !exists {
+			response.Unauthorized(c, "未授权")
+			c.Abort()
+			return
+		}
+
+		user, err := userRepo.GetByID(userID.(string))
+		if err != nil {
+			response.HandleError(c, err, "获取用户信息失败")
+			c.Abort()
+			return
+		}
+
+		if user.VerificationStatus != model.VerificationStatusApproved {
+			response.Forbidden(c, "需要完成身份认证")
+			c.Abort()
+			return
+		}
+
+		c.Next()
+	}
+}