Add download row context menu for pause, resume and cancel

Download row actions were wired only as swipe actions, and
SwipeActionModifier has #if !os(iOS) overloads that return the view
unmodified, so macOS had no way to pause, resume or cancel a download.
The video context menu could not cover it either, since the .downloads
context deliberately hides the built-in cancel item.

Give active download rows their own context menu with pause when queued
or downloading, resume when paused, retry when failed, and a destructive
cancel. Right-click on macOS, long-press on iOS.

Completed rows had a related bug: the delete item called an onDelete
callback that DownloadsView never passed, so it rendered but did nothing
on macOS. Drop the callback and delete via the download manager directly,
which is what already made the same menu work in HomeView.

Claude-Session: https://claude.ai/code/session_0154KH8RAVAvm6iVanhmoW8o

Yattee/Views/Home/HomeView.swift

@@ -1315,11 +1315,6 @@ struct HomeView: View {
                         DownloadRowView(
                             download: download,
                             isActive: false,
-                            onDelete: {
-                                Task {
-                                    await downloadManager?.delete(download)
-                                }
-                            },
                             queueSource: .manual,
                             sourceLabel: String(localized: "queue.source.downloads"),
                             videoList: videoList,