fix：注册界面格式校验修复

src/views/_builtin/login/modules/register.vue

@@ -71,15 +71,38 @@ const securityModel = reactive<SecurityFormModel>({
 // 第一步表单验证规则
 const basicRules = computed<Record<string, Rule | Rule[]>>(() => {
   const validateUsername = async (_rule: Rule, value: string) => {
-    if (value && (value.length < 4 || value.length > 20)) {
+    // 空值检查
+    if (!value) {
+      return Promise.reject(t('page.login.register.usernameRequired'));
+    }
+
+    // 长度检查 (3-20字符)
+    if (value.length < 3 || value.length > 20) {
       return Promise.reject(t('page.login.register.usernameLengthLimit'));
     }
-    if (value) {
+
+    // 格式检查 (只允许字母、数字、下划线)
+    const usernamePattern = /^[a-zA-Z0-9_]+$/;
+    if (!usernamePattern.test(value)) {
+      return Promise.reject(t('page.login.register.usernameFormatError'));
+    }
+
+    // 首字符必须是字母
+    if (!/^[a-zA-Z]/.test(value)) {
+      return Promise.reject(t('page.login.register.usernameStartWithLetter'));
+    }
+
+    // 重复性检查
+    try {
       const { exists } = await authStore.checkUserRepeat({ username: value, authType: 'u' });
       if (exists) {
         return Promise.reject(t('page.login.register.usernameExists'));
       }
+    } catch (error) {
+      console.error('Username validation error:', error);
+      return Promise.reject(t('page.login.register.validationError'));
     }
+
     return Promise.resolve();
   };