chore(comments): re-point dangling supabase/migrations breadcrumbs

The Supabase purge deleted the archived supabase/migrations/.archived/
directory, but 12 src/ files still referenced its files by path in
JSDoc / TODO comments. The references were misleading (pointing to
deleted files), so re-point them at the canonical location of those
RPCs in db/migrations/0001_init.sql. No code or behavior changes.

Also fixed a stray 'supabase shim returns empty results' comment in
src/app/admin/page.tsx (the shim was already removed in Step 3 of
the refactor).

src/actions/shipping/fedex-labels.ts

@@ -93,8 +93,9 @@ async function loadShippingSettingsForBrand(brandId: string): Promise<ShippingSe
 
 /**
  * Calls the legacy `get_order_items_perishable` SECURITY DEFINER RPC
- * via `pool.query`. The function still lives in the database (see
- * supabase/migrations/083_shipping_settings.sql).
+ * via `pool.query`. The function still lives in the database
+ * (originally from the now-archived supabase migrations; consolidated
+ * into `db/migrations/0001_init.sql`).
  */
 async function isShipmentPerishable(orderId: string): Promise<boolean> {
   try {