feat(ui): long-press opens the menus a right-click opens

Every context menu in the app opens from a `contextmenu` event, bound
three different ways across six components -- delegated on a
virtualizer, per row, per card. A phone has no right-click, so a phone
reached none of them (plan 016 B2 phase 3).

This is one document-capture listener installed once from `index.ts`,
not six components' worth of touch handling: a touch that holds still
for 500ms dispatches a synthetic `contextmenu` at the touch point, and
every existing handler runs unchanged. A seam no component has to opt
into is one no future component can forget.

Four details are load-bearing, each a way the obvious version fails.
The target is `composedPath()[0]`, not `elementFromPoint`, which stops
at the outermost shadow host -- every menu here is bound inside one, so
a host-targeted event reaches a delegated listener and no per-row one.
A browser that fires its own long-press `contextmenu` (Chromium does;
WebKit and the Android WebView vary) wins, and ours is told from theirs
by identity rather than `isTrusted`: `isTrusted` works in the app and
is untestable, which would leave the suppression path as the one thing
with no coverage. And the click ending the gesture is swallowed, keyed
on the gesture rather than a time window, or the first tap on the menu
it just opened is eaten too.

The e2e spec presses `.track-row`, not `[role="row"]`: the column
header is a row too, and it is the first one -- a press on it is
correctly ignored, which reads exactly like the gesture not working.

frontend/index.ts

@@ -50,6 +50,7 @@ import '@store/theme-store';
 // registers the document keydown listener for global shortcuts.
 import './src/services/keyboard-shortcut-service';
 import { activateView, deactivateView } from '@utils/view-lifecycle';
+import { installLongPressContextMenu } from '@utils/long-press';
 import {
     hasTrackPayload,
     getDragPayload,
@@ -64,6 +65,11 @@ setBasePath('/dist/webawesome');
 // the session.
 registerBundledIcons();
 
+// The touch equivalent of a right-click, installed once for every menu
+// in the app rather than per component. Harmless on a desktop: it acts
+// on `pointerType === 'touch'` only.
+installLongPressContextMenu();
+
 // ---------------------------------------------------------------------------
 // View caching navigation system
 // ---------------------------------------------------------------------------