feat: loading toasts for all photo actions

Add loading→success/error toast transition to every bulk operation
(archive, restore, delete, approve, add-to-heap, metadata patch).
Also wires gridKeyNav + CauseGroupCard into the bulkAction store so
keyboard-triggered actions show the same per-tile pending/done/error
feedback as BulkActionBar buttons.

web/src/lib/components/sidebar/BulkMetadataSidebar.svelte

@@ -80,11 +80,8 @@
 
 	async function applyMarks(patch: PhotoMark, label: string) {
 		if (busy) return;
+		const tid = toast.loading(`${label}…`);
 		await withBusy(async () => {
-			// Optimistic: patch every selected photo's mark in the local
-			// cache before round-tripping. Sidecar bulk endpoint is
-			// authoritative; on failure we just invalidate so the next
-			// list query overrides.
 			qc.setQueryData<PhotoMarksMap>(['marks'], (prev) => {
 				const map = { ...(prev ?? {}) };
 				for (const id of ids) {
@@ -98,9 +95,9 @@
 			});
 			try {
 				await bulkSetMarks(ids, patch);
-				toast.success(`${label} · ${ids.length}`);
+				toast.success(`${label} · ${ids.length}`, { id: tid });
 			} catch (err) {
-				toast.error(err instanceof Error ? err.message : 'Save failed');
+				toast.error(err instanceof Error ? err.message : 'Save failed', { id: tid });
 				void qc.invalidateQueries({ queryKey: ['marks'] });
 			}
 		});