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/routes/+page.svelte

@@ -714,6 +714,7 @@
       return;
     }
     emptyingArchive = true;
+    const tid = toast.loading("Emptying archive…");
     let total = 0;
     try {
       while (true) {
@@ -729,9 +730,9 @@
         await batchDelete(uids);
         total += uids.length;
       }
-      toast.success(total === 0 ? "Archive already empty" : `Deleted ${total}`);
+      toast.success(total === 0 ? "Archive already empty" : `Deleted ${total}`, { id: tid });
     } catch (err) {
-      toast.error(err instanceof Error ? err.message : "Empty archive failed");
+      toast.error(err instanceof Error ? err.message : "Empty archive failed", { id: tid });
     } finally {
       emptyingArchive = false;
       void qc.invalidateQueries({ queryKey: ["photos"] });