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/stops/manage-stop-products.ts

@@ -4,12 +4,13 @@
  * Assign / unassign a product to a stop.
  *
  * TODO(migration): the `assign_product_to_stop` and
- * `unassign_product_from_stop` SECURITY DEFINER RPCs live in
- * supabase/migrations/030. The RPCs still exist in the database and
- * are called via `pool.query` rather than the Supabase REST gateway.
- * When stops/products are re-platformed on the SaaS rebuild, replace
- * these with direct inserts/deletes on the new `db/schema/stops.ts`
- * `stopProducts` table.
+ * `unassign_product_from_stop` SECURITY DEFINER RPCs (originally from
+ * the now-archived supabase migrations; consolidated into
+ * `db/migrations/0001_init.sql`). The RPCs still exist in the
+ * database and are called via `pool.query`. When stops/products are
+ * re-platformed on the SaaS rebuild, replace these with direct
+ * inserts/deletes on the new `db/schema/stops.ts` `stopProducts`
+ * table.
  */
 
 import { getAdminUser } from "@/lib/admin-permissions";