新增客户标签库：管理员维护、员工选择

租户级标签 CRUD 与颜色预设；客户打标仅能从库中选择，设置页提供管理入口，列表筛选随标签库动态生成。

server/internal/handler/customer.go

@@ -91,6 +91,16 @@ func (h *CustomerHandler) Create(c *gin.Context) {
 	}
 
 	customer.TenantID = middleware.GetTenantID(c)
+	if customer.Tags != "" {
+		normalized, err := normalizeCustomerTagsForTenant(customer.TenantID, customer.Tags, nil)
+		if err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
+			return
+		}
+		customer.Tags = normalized
+	} else {
+		customer.Tags = "[]"
+	}
 
 	if err := model.DB.Create(&customer).Error; err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "创建失败"})
@@ -130,6 +140,14 @@ func (h *CustomerHandler) Update(c *gin.Context) {
 		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "没有可更新字段"})
 		return
 	}
+	if raw, ok := updates["tags"]; ok {
+		normalized, err := normalizeCustomerTagsForTenant(tenantID, raw, parseCustomerTagsJSON(customer.Tags))
+		if err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
+			return
+		}
+		updates["tags"] = normalized
+	}
 
 	if err := model.DB.Model(&customer).Updates(updates).Error; err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "更新失败"})