Fully implement Kavenegar SMS support

Core changes:
- ISmsService: add SendBulkAsync (batches of 200) + GetAccountInfoAsync
- KavenegarSmsService: POST requests, sender number config, bulk send
  via comma-separated receptors, account balance, full error code mapping
  (HTTP 400-432), enabled-flag check before any send
- SmsMarketingService: replaced per-recipient loop with SendBulkAsync
- SmsController: new GET /sms/balance endpoint returns Kavenegar credit
- SmsDtos: SmsBalanceDto
- IntegrationDtos + PlatformIntegrationService: SenderNumber field
- appsettings.json + docker-compose: Kavenegar__SenderNumber = 90005671

Dashboard:
- sms-screen: char counter, SMS parts indicator (Persian 70/67 chars,
  Latin 160/153), account balance card, sender line display, result banner

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/dashboard/messages/en.json

@@ -378,7 +378,16 @@
     "usage": "Usage this month",
     "unlimited": "Unlimited",
     "sent": "Sent",
-    "failed": "Failed"
+    "failed": "Failed",
+    "charCount": "{count} chars",
+    "smsPartsHint": "{parts} SMS",
+    "balance": "Account credit",
+    "balanceAmount": "{amount} Rials",
+    "balanceNotConfigured": "Kavenegar not configured",
+    "sender": "Sender line",
+    "recipientsCount": "{count} recipients",
+    "sendConfirm": "Send to {count} people?",
+    "sending": "Sending..."
   },
   "reports": {
     "title": "Reports & analytics",

web/dashboard/messages/fa.json

@@ -378,7 +378,16 @@
     "usage": "مصرف این ماه",
     "unlimited": "نامحدود",
     "sent": "ارسال شد",
-    "failed": "ناموفق"
+    "failed": "ناموفق",
+    "charCount": "{count} حرف",
+    "smsPartsHint": "{parts} پیامک",
+    "balance": "اعتبار حساب",
+    "balanceAmount": "{amount} ریال",
+    "balanceNotConfigured": "Kavenegar پیکربندی نشده",
+    "sender": "خط فرستنده",
+    "recipientsCount": "{count} مخاطب",
+    "sendConfirm": "ارسال به {count} نفر؟",
+    "sending": "در حال ارسال..."
   },
   "reports": {
     "title": "گزارش‌ها و تحلیل",