[backend/core] Also use the NoteService KeyedLocker when it's called from ActivityHandlerService

This fixes sporadic "Unique constraint violation" exceptions on the "IX_note_uri" index.

Iceshrimp.Backend/Core/Federation/ActivityPub/ActivityHandlerService.cs

@@ -105,6 +105,7 @@ public class ActivityHandlerService(
 		activity.Object = await objectResolver.ResolveObject(activity.Object, actor.Uri) as ASNote ??
 		                  throw GracefulException.UnprocessableEntity("Failed to resolve create object");
 
+		using (await NoteService.GetNoteProcessLockAsync(activity.Object.Id))
 			await noteSvc.ProcessNoteAsync(activity.Object, actor, inboxUser);
 	}
 
@@ -335,6 +336,7 @@ public class ActivityHandlerService(
 				await userSvc.UpdateUserAsync(resolvedActor, actor);
 				break;
 			case ASNote note:
+				using (await NoteService.GetNoteProcessLockAsync(note.Id))
 					await noteSvc.ProcessNoteUpdateAsync(note, resolvedActor);
 				break;
 			default:

Iceshrimp.Backend/Core/Services/NoteService.cs

@@ -715,6 +715,8 @@ public class NoteService(
 			eventSvc.RaiseNoteDeleted(this, hit);
 	}
 
+	public static ValueTask<IDisposable> GetNoteProcessLockAsync(string uri) => KeyedLocker.LockAsync(uri);
+
 	public async Task<Note?> ProcessNoteAsync(ASNote note, User actor, User? user = null)
 	{
 		var dbHit = await db.Notes.IncludeCommonProperties().FirstOrDefaultAsync(p => p.Uri == note.Id);