[Demo] Add admin demo-mode toggle + generic website ingest source

- AppSetting: DemoMode, WebsitesEnabled, WebsiteUrls
- Facility.IsDemo flag; SeedData split into SeedReferenceAsync (always)
  + SeedDemoAsync/ClearDemoAsync (idempotent, toggleable at runtime)
- WebsiteListingSource: scrape any admin-configured URL (og:title + content)
- Admin Settings: seed/clear demo card, demo-mode checkbox, website source
  fields; Program.cs seeds demo when DemoMode on (or in Development)
- EF migration DemoModeAndWebsites

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

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

@@ -1,3 +1,4 @@
+using JobsMedical.Web.Data;
 using JobsMedical.Web.Models;
 using JobsMedical.Web.Services;
 using JobsMedical.Web.Services.Scraping;
@@ -12,10 +13,12 @@ public class SettingsModel : PageModel
 {
     private readonly SettingsService _settings;
     private readonly ISmsSender _sms;
-    public SettingsModel(SettingsService settings, ISmsSender sms)
+    private readonly AppDbContext _db;
+    public SettingsModel(SettingsService settings, ISmsSender sms, AppDbContext db)
     {
         _settings = settings;
         _sms = sms;
+        _db = db;
     }
 
     [BindProperty] public IngestionMode Mode { get; set; }
@@ -48,8 +51,12 @@ public class SettingsModel : PageModel
     [BindProperty] public string? VapidPrivateKey { get; set; }
     [BindProperty] public string? VapidSubject { get; set; }
     [BindProperty] public string? TestPhone { get; set; }
+    [BindProperty] public bool DemoMode { get; set; }
+    [BindProperty] public bool WebsitesEnabled { get; set; }
+    [BindProperty] public string? WebsiteUrls { get; set; }
     [TempData] public string? Saved { get; set; }
     [TempData] public string? SmsTest { get; set; }
+    [TempData] public string? DemoMsg { get; set; }
 
     public async Task OnGetAsync()
     {
@@ -78,6 +85,9 @@ public class SettingsModel : PageModel
         SmsTemplate = s.SmsTemplate;
         SmsSender = s.SmsSender;
         NeshanMapKey = s.NeshanMapKey;
+        DemoMode = s.DemoMode;
+        WebsitesEnabled = s.WebsitesEnabled;
+        WebsiteUrls = s.WebsiteUrls;
         PushEnabled = s.PushEnabled;
         VapidPublicKey = s.VapidPublicKey;
         VapidPrivateKey = s.VapidPrivateKey;
@@ -112,6 +122,9 @@ public class SettingsModel : PageModel
             SmsTemplate = SmsTemplate,
             SmsSender = SmsSender,
             NeshanMapKey = NeshanMapKey,
+            DemoMode = DemoMode,
+            WebsitesEnabled = WebsitesEnabled,
+            WebsiteUrls = WebsiteUrls,
             PushEnabled = PushEnabled,
             VapidPublicKey = VapidPublicKey,
             VapidPrivateKey = VapidPrivateKey,
@@ -121,6 +134,20 @@ public class SettingsModel : PageModel
         return RedirectToPage();
     }
 
+    public async Task<IActionResult> OnPostSeedDemoAsync()
+    {
+        var n = await SeedData.SeedDemoAsync(_db);
+        DemoMsg = n > 0 ? $"داده‌های نمونه ثبت شد ({n} مرکز + شیفت/استخدام)." : "داده‌های نمونه از قبل موجود است.";
+        return RedirectToPage();
+    }
+
+    public async Task<IActionResult> OnPostClearDemoAsync()
+    {
+        var n = await SeedData.ClearDemoAsync(_db);
+        DemoMsg = $"داده‌های نمونه حذف شد ({n} مرکز و آگهی‌های وابسته).";
+        return RedirectToPage();
+    }
+
     public async Task<IActionResult> OnPostTestSmsAsync()
     {
         var s = await _settings.GetAsync();