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/Services/NotificationService.cs

@@ -0,0 +1,78 @@
+using JobsMedical.Web.Data;
+using JobsMedical.Web.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace JobsMedical.Web.Services;
+
+/// <summary>
+/// In-app notifications. When a new shift/job is published, notifies users whose saved
+/// preferences match it (role / city / — for shifts — shift type). Users with no preference set
+/// are NOT notified (avoids spamming everyone). One notification per matching user.
+/// </summary>
+public class NotificationService
+{
+    private readonly AppDbContext _db;
+    private readonly ILogger<NotificationService> _log;
+
+    public NotificationService(AppDbContext db, ILogger<NotificationService> log)
+    {
+        _db = db;
+        _log = log;
+    }
+
+    public Task<int> UnreadCountAsync(int userId) =>
+        _db.Notifications.CountAsync(n => n.UserId == userId && !n.IsRead);
+
+    public Task<List<Notification>> ListAsync(int userId, int take = 50) =>
+        _db.Notifications.Where(n => n.UserId == userId)
+            .OrderByDescending(n => n.CreatedAt).Take(take).ToListAsync();
+
+    public async Task MarkAllReadAsync(int userId) =>
+        await _db.Notifications.Where(n => n.UserId == userId && !n.IsRead)
+            .ExecuteUpdateAsync(s => s.SetProperty(n => n.IsRead, true));
+
+    public async Task NotifyNewShiftAsync(int shiftId)
+    {
+        var s = await _db.Shifts.Include(x => x.Facility).Include(x => x.Role)
+            .FirstOrDefaultAsync(x => x.Id == shiftId);
+        if (s is null) return;
+
+        var users = await MatchingUserIdsAsync(s.RoleId, s.Facility.CityId, s.ShiftType);
+        var title = $"شیفت جدید: {s.Role.Name}";
+        var body = $"{s.Facility.Name} — {JalaliDate.WeekDayName(s.Date)} {JalaliDate.Time(s.StartTime)}";
+        await AddAsync(users, title, body, $"/Shifts/Details/{s.Id}");
+    }
+
+    public async Task NotifyNewJobAsync(int jobId)
+    {
+        var j = await _db.JobOpenings.Include(x => x.Facility).Include(x => x.Role)
+            .FirstOrDefaultAsync(x => x.Id == jobId);
+        if (j is null) return;
+
+        var users = await MatchingUserIdsAsync(j.RoleId, j.Facility.CityId, null);
+        await AddAsync(users, $"استخدام جدید: {j.Title}", j.Facility.Name, $"/Jobs/Details/{j.Id}");
+    }
+
+    /// <summary>Users with a non-empty preference that matches the listing (via their visitor link).</summary>
+    private async Task<List<int>> MatchingUserIdsAsync(int roleId, int cityId, ShiftType? shiftType)
+    {
+        var q = from up in _db.UserPreferences
+                join v in _db.Visitors on up.VisitorId equals v.Id
+                where v.UserId != null
+                    && (up.RoleId != null || up.CityId != null)            // must have a real preference
+                    && (up.RoleId == null || up.RoleId == roleId)
+                    && (up.CityId == null || up.CityId == cityId)
+                    && (shiftType == null || up.PreferredShiftType == null || up.PreferredShiftType == shiftType)
+                select v.UserId!.Value;
+        return await q.Distinct().ToListAsync();
+    }
+
+    private async Task AddAsync(List<int> userIds, string title, string? body, string url)
+    {
+        if (userIds.Count == 0) return;
+        foreach (var uid in userIds)
+            _db.Notifications.Add(new Notification { UserId = uid, Title = title, Body = body, Url = url });
+        await _db.SaveChangesAsync();
+        _log.LogInformation("Notified {Count} users: {Title}", userIds.Count, title);
+    }
+}