Add SEO sitemap/robots + real SMS OTP (Kavenegar, admin-configured)

- /sitemap.xml (static pages + open shifts + fresh jobs, respecting expiry) + /robots.txt (blocks /Admin,/Employer); base URL from forwarded request → https://hamkadr.ir in prod
- ISmsSender + KavenegarSmsSender (verify/lookup template, sms/send fallback); SMS settings (enabled/apikey/template/sender) in /Admin/Settings; OtpService.IssueAsync sends SMS and stops revealing the code when enabled (dev still shows it); migration

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

src/JobsMedical.Web/Pages/Admin/Settings.cshtml.cs

@@ -32,6 +32,10 @@ public class SettingsModel : PageModel
     [BindProperty] public string? DivarQueries { get; set; }
     [BindProperty] public bool MedjobsEnabled { get; set; }
     [BindProperty] public int MedjobsMaxAds { get; set; } = 40;
+    [BindProperty] public bool SmsEnabled { get; set; }
+    [BindProperty] public string? SmsApiKey { get; set; }
+    [BindProperty] public string? SmsTemplate { get; set; }
+    [BindProperty] public string? SmsSender { get; set; }
     [TempData] public string? Saved { get; set; }
 
     public async Task OnGetAsync()
@@ -56,6 +60,10 @@ public class SettingsModel : PageModel
         DivarQueries = s.DivarQueries;
         MedjobsEnabled = s.MedjobsEnabled;
         MedjobsMaxAds = s.MedjobsMaxAds;
+        SmsEnabled = s.SmsEnabled;
+        SmsApiKey = s.SmsApiKey;
+        SmsTemplate = s.SmsTemplate;
+        SmsSender = s.SmsSender;
     }
 
     public async Task<IActionResult> OnPostAsync()
@@ -81,6 +89,10 @@ public class SettingsModel : PageModel
             DivarQueries = DivarQueries,
             MedjobsEnabled = MedjobsEnabled,
             MedjobsMaxAds = MedjobsMaxAds,
+            SmsEnabled = SmsEnabled,
+            SmsApiKey = SmsApiKey,
+            SmsTemplate = SmsTemplate,
+            SmsSender = SmsSender,
         });
         Saved = "تنظیمات ذخیره شد.";
         return RedirectToPage();