Notify matching users when a new shift/job is posted (in-app notifications)

- Notification entity + NotificationService: on publish, notify users whose saved prefs match the listing (role/city/+shift type); users with no preference aren't spammed
- Wired into PostShift, PostJob, and Admin Review publish
- 🔔 bell with unread count in the header (@inject) + /Me/Notifications page (mark-all-read on open)
- Reliable in-app delivery (works in Iran without FCM); Web Push can ride the same records later
- Verified: employee pref → employer posts matching shift → employee bell=۱ + 'شیفت جدید: پزشک عمومی'

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

src/JobsMedical.Web/Program.cs

@@ -23,6 +23,7 @@ builder.Services.AddSingleton<ISmsSender, KavenegarSmsSender>();
 builder.Services.AddScoped<OtpService>();
 builder.Services.AddSingleton<CaptchaService>();
 builder.Services.AddScoped<SubmissionGuard>();
+builder.Services.AddScoped<NotificationService>();
 // Listing parser: heuristic now; swap for an LLM-backed IListingParser later.
 builder.Services.AddSingleton<IListingParser, HeuristicListingParser>();