Wire Web Push broadcaster: lock-screen pushes ride the in-app notifications

- nuget.config with Soroush Nexus + Liara mirrors (nuget.org filtered); added WebPush 1.0.12
- PushNotifier: VAPID send to a user's subscriptions, prunes dead (404/410); config from AppSetting
- NotificationService fans out a Web Push to matched users' subscribed browsers after creating in-app notifications (best-effort; no-op until admin enables push + sets VAPID)
- Build verified through the mirrors; app boots with PushNotifier wired

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

src/JobsMedical.Web/Program.cs

@@ -24,6 +24,7 @@ builder.Services.AddScoped<OtpService>();
 builder.Services.AddSingleton<CaptchaService>();
 builder.Services.AddScoped<SubmissionGuard>();
 builder.Services.AddScoped<NotificationService>();
+builder.Services.AddScoped<PushNotifier>();
 // Listing parser: heuristic now; swap for an LLM-backed IListingParser later.
 builder.Services.AddSingleton<IListingParser, HeuristicListingParser>();