feat(sms): bring-your-own-provider — cafés use their own SMS account

The platform no longer sells SMS. Each café saves its OWN Kavenegar API
key + sender line (new Cafes columns + migration) and campaigns are sent
and billed through that account.

Backend:
- GET/PUT /sms/settings (Manager/Owner; key echoed masked, verified
  against the provider before saving)
- campaign + balance use the café's credentials; SMS_NOT_CONFIGURED
  error when missing; plan-tier SMS gating removed everywhere
  (PlanLimitChecker, SmsMarketingService, billing status)
- platform Kavenegar config stays ONLY for login OTPs (env/DB)
- design-time DbContext factory so `dotnet ef migrations add` works
  without booting the host

Dashboard:
- SMS screen: provider-settings card, not-configured callout, campaign
  form disabled until configured; quota bar removed (usage stays as info)
- subscription screen + plan comparison no longer show SMS limits

Admin panel:
- Kavenegar/SMS section removed from integrations (request field now
  optional; stored OTP config untouched)
- SMS limit field removed from the plan editor
- nav label "درگاه و پیامک" → "درگاه پرداخت و AI"

fa/en/ar translations. 86 tests pass; all tsc clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/dashboard/messages/ar.json

@@ -481,10 +481,36 @@
     "targetGroup": "المجموعة المستهدفة",
     "allCustomers": "كل العملاء",
     "send": "إرسال",
-    "usage": "الاستخدام هذا الشهر",
+    "usage": "المُرسَل هذا الشهر",
     "unlimited": "غير محدود",
     "sent": "تم الإرسال",
-    "failed": "فشل"
+    "failed": "فشل",
+    "charCount": "{count} حرفاً",
+    "smsPartsHint": "{parts} رسالة",
+    "balance": "رصيد حسابك",
+    "balanceAmount": "{amount} ريال",
+    "balanceNotConfigured": "خدمة SMS غير مفعّلة",
+    "sender": "خط الإرسال",
+    "recipientsCount": "{count} مستلماً",
+    "sendConfirm": "إرسال إلى {count} شخصاً؟",
+    "sending": "جارٍ الإرسال...",
+    "byoHint": "تُرسل الرسائل عبر حسابك وخطك الخاص — تُحتسب تكلفة الإرسال مباشرة لدى مزوّد SMS الخاص بك.",
+    "notConfiguredOwner": "لإرسال الرسائل، احفظ أولاً مفتاح API ورقم خط كاوه‌نگار في الإعدادات أعلاه.",
+    "notConfiguredStaff": "لم يقم مدير المقهى بإعداد خدمة SMS بعد.",
+    "settings": {
+      "title": "إعدادات مزوّد SMS",
+      "hint": "أنشئ مفتاح API من لوحة كاوه‌نگار (kavenegar.com) وأدخله مع رقم خط الإرسال.",
+      "apiKey": "مفتاح API",
+      "apiKeyPlaceholder": "API Key",
+      "senderNumber": "رقم خط الإرسال",
+      "senderPlaceholder": "10004346...",
+      "configured": "خدمة SMS مفعّلة.",
+      "notConfigured": "لم يتم الإعداد بعد.",
+      "save": "حفظ",
+      "saving": "جارٍ التحقق…",
+      "saved": "تم حفظ إعدادات SMS.",
+      "saveFailed": "مفتاح API غير صالح أو فشل الحفظ."
+    }
   },
   "reports": {
     "title": "التقارير والتحليلات",