fix(frontend): make Escape dismiss overlays before clearing selection

Escape now peels one layer at a time on the files page: an open tag
editor, pool picker, or delete confirm closes first, and only a second
Escape drops the multi-select. Selection-exit handling moves out of
SelectionBar into a single window handler on the page so precedence is
deterministic rather than dependent on window-listener fire order.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/components/layout/SelectionBar.svelte

@@ -8,14 +8,8 @@
 	}
 
 	let { onEditTags, onAddToPool, onDelete }: Props = $props();
-
-	function handleKeydown(e: KeyboardEvent) {
-		if (e.key === 'Escape') selectionStore.exit();
-	}
 </script>
 
-<svelte:window onkeydown={handleKeydown} />
-
 <div class="bar" role="toolbar" aria-label="Selection actions">
 	<div class="row">
 		<!-- Count / deselect all -->