feat(api): 新增邮箱注册检查接口

- 新增 /checkEmailRegistered GET 接口，用于检查邮箱是否已注册
- 实现邮箱格式校验，保证输入的邮箱地址有效
- 查询邮箱注册的账户列表，统计账号数量并返回是否已注册
- 返回结果封装在 CheckEmailResult 类中，包含注册状态及账号数量
- 在 SecurityConfig 中添加 /api/checkEmailRegistered 接口白名单配置

src/main/java/com/gxwebsoft/common/core/security/SecurityConfig.java

@@ -47,6 +47,7 @@ public class SecurityConfig extends WebSecurityConfigurerAdapter {
                         "/api/findAccountByPhone",
                         "/api/resetPassword",
                         "/api/checkPhoneRegistered",
+                        "/api/checkEmailRegistered",
                         "/api/existence",
                         "/api/oss/upload",
                         "/druid/**",

src/main/java/com/gxwebsoft/common/system/controller/MainController.java

@@ -44,6 +44,7 @@ import com.gxwebsoft.common.system.result.CaptchaResult;
 import com.gxwebsoft.common.system.result.LoginResult;
 import com.gxwebsoft.common.system.result.TenantOption;
 import com.gxwebsoft.common.system.result.AccountInfoResult;
+import com.gxwebsoft.common.system.result.CheckEmailResult;
 import com.gxwebsoft.common.system.result.CheckPhoneResult;
 import com.gxwebsoft.common.system.service.*;
 import com.gxwebsoft.common.system.mapper.UserMapper;
@@ -1788,6 +1789,20 @@ public class MainController extends BaseController {
    * 检查手机号是否已注册（可选接口）
    */
   @Operation(summary = "检查手机号是否已注册")
+  @GetMapping("/checkEmailRegistered")
+  public ApiResult<?> checkEmailRegistered(@RequestParam("email") String email) {
+    // 邮箱格式校验
+    if (!CommonUtil.isValidEmail(email)) {
+      return fail("请输入有效的邮箱地址");
+    }
+    // 统计该邮箱注册的账号数量（跨租户，复用 findAccountsByEmail）
+    List<User> accounts = userService.findAccountsByEmail(email);
+    CheckEmailResult result = new CheckEmailResult();
+    result.setIsRegistered(accounts != null && !accounts.isEmpty());
+    result.setAccountCount(accounts != null ? accounts.size() : 0);
+    return success(result);
+  }
+
   @GetMapping("/checkPhoneRegistered")
   public ApiResult<?> checkPhoneRegistered(@RequestParam("phone") String phone) {
     // 验证手机号

src/main/java/com/gxwebsoft/common/system/result/CheckEmailResult.java

@@ -0,0 +1,28 @@
+package com.gxwebsoft.common.system.result;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.io.Serializable;
+
+/**
+ * 检查邮箱返回结果
+ *
+ * @author WebSoft
+ * @since 2026-08-06
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Schema(description = "检查邮箱返回结果")
+public class CheckEmailResult implements Serializable {
+    private static final long serialVersionUID = 1L;
+
+    @Schema(description = "是否已注册")
+    private Boolean isRegistered;
+
+    @Schema(description = "账号数量")
+    private Integer accountCount;
+}