Make CloudKit apply path scope-aware and re-upload local-newer merges

CloudKit record names carry a source scope suffix so the same channel
or video ID can exist under different sources, but the apply path
matched local entities by bare ID: incoming records could merge into an
entity from a different scope, and a remote deletion of one scope
deleted every local entity with that ID and cascaded scoped deletions
for all other scopes back to CloudKit.

- Match local entities on the full mapper-derived record name when
  merging incoming records, materializing records for upload, and
  applying remote deletions.
- Remote deletions now remove only the matching entity and no longer
  queue CloudKit deletions (no echo, no cross-scope cascade).
- Insert dedupe for CloudKit-applied records is scope-aware, so a
  same-ID record from a different source inserts instead of being
  silently dropped. Remotely added bookmarks also update the
  fast-lookup cache immediately.
- When conflict resolution during a fetch keeps newer local data, the
  merge result is queued for upload; previously the server (and other
  devices) kept the stale version unless the entity was edited again.
  Strict timestamp comparisons prevent re-upload ping-pong between
  devices.

Yattee/Data/DataManager+ChannelNotificationSettings.swift

@@ -115,6 +115,22 @@ extension DataManager {
         }
     }
 
+    /// Gets all notification settings matching a channel ID. The same ID can
+    /// exist under multiple source scopes.
+    func allChannelNotificationSettings(forChannelID channelID: String) -> [ChannelNotificationSettings] {
+        let descriptor = FetchDescriptor<ChannelNotificationSettings>(
+            predicate: #Predicate { $0.channelID == channelID }
+        )
+        return (try? modelContext.fetch(descriptor)) ?? []
+    }
+
+    /// Deletes a single notification settings record without queueing a
+    /// CloudKit deletion. Used by CloudKitSyncEngine when applying remote deletions.
+    func deleteChannelNotificationSettings(_ settings: ChannelNotificationSettings) {
+        modelContext.delete(settings)
+        save()
+    }
+
     /// Deletes notification settings for a channel.
     /// - Parameter channelID: The channel ID to delete settings for.
     func deleteNotificationSettings(for channelID: String) {