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/en.json

@@ -500,19 +500,36 @@
     "targetGroup": "Target group",
     "allCustomers": "All customers",
     "send": "Send",
-    "usage": "Usage this month",
+    "usage": "Sent this month",
     "unlimited": "Unlimited",
     "sent": "Sent",
     "failed": "Failed",
     "charCount": "{count} chars",
     "smsPartsHint": "{parts} SMS",
-    "balance": "Account credit",
+    "balance": "Your account credit",
     "balanceAmount": "{amount} Rials",
-    "balanceNotConfigured": "Kavenegar not configured",
+    "balanceNotConfigured": "SMS service not set up",
     "sender": "Sender line",
     "recipientsCount": "{count} recipients",
     "sendConfirm": "Send to {count} people?",
-    "sending": "Sending..."
+    "sending": "Sending...",
+    "byoHint": "SMS is sent through your OWN provider account and line — sending costs are billed directly by your SMS provider.",
+    "notConfiguredOwner": "To send SMS, first save your Kavenegar API key and sender line in the settings above.",
+    "notConfiguredStaff": "The SMS service has not been set up by the café manager yet.",
+    "settings": {
+      "title": "SMS provider settings",
+      "hint": "Create an API key in your Kavenegar panel (kavenegar.com) and enter it with your sender line number.",
+      "apiKey": "Kavenegar API key",
+      "apiKeyPlaceholder": "API Key",
+      "senderNumber": "Sender line number",
+      "senderPlaceholder": "10004346...",
+      "configured": "SMS service is active.",
+      "notConfigured": "Not set up yet.",
+      "save": "Save",
+      "saving": "Verifying…",
+      "saved": "SMS settings saved.",
+      "saveFailed": "The API key is invalid or saving failed."
+    }
   },
   "reports": {
     "title": "Reports & analytics",