revert: restore wx_unionid (database schema fix required)

@@ -274,24 +274,25 @@ class AuthService
         if ($user) {
             // 更新 openid
             if ($openid && $user['wx_openid'] !== $openid) {
-                $stmt = $this->pdo->prepare("UPDATE users SET wx_openid = ? WHERE id = ?");
-                $stmt->execute([$openid, $user['id']]);
+                $stmt = $this->pdo->prepare("UPDATE users SET wx_openid = ?, wx_unionid = ? WHERE id = ?");
+                $stmt->execute([$openid, $unionid, $user['id']]);
             }
             return $user;
         }
 
         // 创建新用户
         $stmt = $this->pdo->prepare("
-            INSERT INTO users (phone, wx_openid, nickname)
-            VALUES (?, ?, ?)
+            INSERT INTO users (phone, wx_openid, wx_unionid, nickname)
+            VALUES (?, ?, ?, ?)
         ");
         $nickname = '用户' . substr($phone, -4);
-        $stmt->execute([$phone, $openid, $nickname]);
+        $stmt->execute([$phone, $openid, $unionid, $nickname]);
 
         return [
             'id' => $this->pdo->lastInsertId(),
             'phone' => $phone,
             'wx_openid' => $openid,
+            'wx_unionid' => $unionid,
             'nickname' => $nickname,
             'avatar_url' => null,
         ];