fix: notification pushes now match what the 2023 client reads

Most pushes were still shaped for the 2020 watch, so the 2023 client
parsed them as empty or dropped them without any error.

- RelationshipChanged carries the relationship row, to both players, on
  friend request / accept / remove / add and on favorite / mute / ignore.
  Friend requests and accepts also land in the notifications inbox.
- ModerationKick uses the client's flat moderation block, with the
  reason in VoteKickReason (the only field the dialog shows).
- Bans, account deletion, password resets and second-session takeover
  are a Logout with a numeric reason instead of a kick to the dorm; the
  old string reason failed the client's parse.
- SubscribeToPlayers is honoured: each connection joins a presence group
  per subscribed player, and presence (only presence) reaches subscribers
  as well as friends. The hub allows 180 s of client silence, since the
  client reconnects at most 3 times per login.
- Admin broadcast sends its text as a coach message and can start the
  client's own maintenance countdown; ServerMaintenance only reads
  StartsInMinutes.
- ConsumableMapping, StorefrontBalance, gift, player event, level-up,
  RoomUpdate, profile-image and PlayerLeftChat pushes carry the client's
  DTOs. "Join rejected" is the client's RequestGameInvite message.

Contract in docs/recroom-2023-notifications.md; push frames are checked
by NotificationContractTests through a capturing hub context.

DorkNet.Server/Controllers/API/Relationships/V2/RelationshipsController.cs

@@ -48,7 +48,11 @@ namespace DorkNet.Server.Controllers.API.Relationships.V2;
 /// </summary>
 [ApiController]
 [Authorize]
-public class RelationshipsController(DorkNetDbContext db, NotificationService notifications, ServerSettingsService settings) : ControllerBase
+public class RelationshipsController(
+    DorkNetDbContext db,
+    NotificationService notifications,
+    SystemNotificationService systemNotifications,
+    ServerSettingsService settings) : ControllerBase
 {
     // RelationshipType — int values match Relationship.RelationshipType
     // in the patched dump.cs.
@@ -226,7 +230,9 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
         }
         await db.SaveChangesAsync();
 
-        await notifications.FriendRequestReceived(id, me);
+        await PushPairAsync(me, id);
+        // The "X sent you a friend request" row in the target's notifications.
+        await systemNotifications.SendAsync(id, SystemNotificationService.MessageType.FriendInvite, fromPlayerId: me);
         return Ok(BuildRelationship(row, me));
     }
 
@@ -251,7 +257,8 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
         rel.UpdatedAt = DateTime.UtcNow;
         await db.SaveChangesAsync();
 
-        await notifications.FriendRequestAccepted(id, me);
+        await PushPairAsync(me, id);
+        await systemNotifications.SendAsync(id, SystemNotificationService.MessageType.FriendRequestAccepted, fromPlayerId: me);
         return Ok(BuildRelationship(rel, me));
     }
 
@@ -285,7 +292,7 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
 
         db.Relationships.RemoveRange(removable);
         await db.SaveChangesAsync();
-        await notifications.FriendRemoved(id, me);
+        await PushPairAsync(me, id);
 
         var remaining = pair.Except(removable).ToList();
         return Ok(remaining.Count == 0 ? EmptyRelationship(id) : BuildMerged(me, id, remaining));
@@ -333,6 +340,8 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
             existing.UpdatedAt = DateTime.UtcNow;
         }
         await db.SaveChangesAsync();
+        await PushPairAsync(me, id);
+        await systemNotifications.SendAsync(id, SystemNotificationService.MessageType.FriendRequestAccepted, fromPlayerId: me);
         return Ok(BuildRelationship(existing, me));
     }
 
@@ -411,6 +420,10 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
         if (ignored is bool i) row.Ignored = i;
         row.UpdatedAt = DateTime.UtcNow;
         await db.SaveChangesAsync();
+        // The HTTP reply is only an ack; the updated row reaches the client
+        // through RelationshipChanged. A preference is the caller's own bit,
+        // so only the caller is told.
+        await PushPairAsync(me, otherId, notifyOther: false);
         return Ok(new Models.Auth.RecNetResult { Success = true, Error = string.Empty });
     }
 
@@ -511,6 +524,36 @@ public class RelationshipsController(DorkNetDbContext db, NotificationService no
 
     // ── helpers ──────────────────────────────────────────────────────
 
+    /// <summary>Push RelationshipChanged for the pair (<paramref name="me"/>,
+    /// <paramref name="other"/>) after a change, each side getting its OWN view
+    /// of the relationship. Without this a friend request, accept or unfriend
+    /// only showed up after the friends list was refetched, and the client
+    /// never re-subscribed to the new friend's presence.</summary>
+    private async Task PushPairAsync(long me, long other, bool notifyOther = true)
+    {
+        var pair = await db.Relationships
+            .Where(r => (r.RequesterId == me && r.TargetId == other) ||
+                        (r.RequesterId == other && r.TargetId == me))
+            .ToListAsync();
+        var globalFriends = await settings.IsGlobalFriendsEnabledAsync();
+
+        await notifications.RelationshipChanged(me, ViewOf(me, other, pair, globalFriends));
+        if (notifyOther)
+            await notifications.RelationshipChanged(other, ViewOf(other, me, pair, globalFriends));
+    }
+
+    /// <summary>The relationship from <paramref name="viewer"/>'s side, the way
+    /// <c>v2/get</c> would list it.</summary>
+    private static Dictionary<string, object> ViewOf(
+        long viewer, long other, List<RelationshipEntity> pair, bool globalFriends)
+    {
+        if (globalFriends
+            && other != RelationshipQueries.SystemAccountId
+            && !pair.Any(r => r.Status == EntityStatus.Blocked))
+            return SynthFriend(other, pair.FirstOrDefault(r => r.RequesterId == viewer), viewer);
+        return pair.Count == 0 ? EmptyRelationship(other) : BuildMerged(viewer, other, pair);
+    }
+
     private async Task<HashSet<long>> FriendIdsAsync(long playerId)
     {
         var rows = await db.Relationships