feat(auth): add MizbanSMS OTP provider with per-flow messages and signup recovery

- Add MizbanSMS as selectable SMS provider (SMS_PROVIDER), keep Kavenegar
- Distinct OTP wording per flow via OtpMessageKind (register/login/change-phone)
- register() resumes an unverified account instead of blocking re-registration
- Hourly cleanup of abandoned unverified accounts (>24h) + expired OTP codes

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/config/configuration.ts

@@ -84,10 +84,37 @@ export default () => ({
     port: parseInt(process.env.REDIS_PORT || '6379', 10),
   },
 
-  // OTP SMS via Kavenegar (verify/lookup template API).
+  // OTP SMS. Provider selectable via SMS_PROVIDER ('mizbansms' | 'kavenegar').
   sms: {
+    provider: (process.env.SMS_PROVIDER || 'mizbansms').trim().toLowerCase(),
+
+    // Kavenegar (verify/lookup template API) — kept for fallback.
     kavenegarApiKey: process.env.KAVENEGAR_API_KEY || '',
     kavenegarOtpTemplate: process.env.KAVENEGAR_OTP_TEMPLATE || '',
+
+    // MizbanSMS (services.mizbansms.com) — sends full message text over a
+    // dedicated line, so the OTP wording is composed here, not from a template.
+    mizban: {
+      baseUrl: process.env.MIZBANSMS_BASE_URL || 'http://services.mizbansms.com',
+      username: process.env.MIZBANSMS_USERNAME || '',
+      password: process.env.MIZBANSMS_PASSWORD || '',
+      from: process.env.MIZBANSMS_FROM || '5000467254',
+      api: parseInt(process.env.MIZBANSMS_API || '2016', 10),
+      userType: parseInt(process.env.MIZBANSMS_USERTYPE || '2', 10),
+      // Per-message-kind wording. `{code}` (or `{{CODE}}`) is replaced with the
+      // 6-digit OTP. \n is allowed for multi-line messages.
+      templates: {
+        register:
+          process.env.MIZBANSMS_OTP_TEMPLATE_REGISTER ||
+          'به ابربان خوش آمدید.\nکد تأیید شما: {code}',
+        login:
+          process.env.MIZBANSMS_OTP_TEMPLATE_LOGIN ||
+          'رمز یکبار مصرف ابربان:\n{code}',
+        changePhone:
+          process.env.MIZBANSMS_OTP_TEMPLATE_CHANGE_PHONE ||
+          'کد تأیید شماره جدید ابربان:\n{code}',
+      },
+    },
   },
 
   registry: {