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/analytics.ts

@@ -68,9 +68,10 @@ export type ConversionFunnel = {
 
 /**
  * Aggregate KPIs over a date window. Replaces the
- * `get_reports_summary` SECURITY DEFINER RPC from
- * `supabase/migrations/031_reports_v1_rpcs.sql`. Returns zeroed metrics
- * if the caller is unauthenticated or no orders exist in the window.
+ * `get_reports_summary` SECURITY DEFINER RPC (originally from the now-
+ * archived supabase migrations; consolidated into
+ * `db/migrations/0001_init.sql`). Returns zeroed metrics if the caller
+ * is unauthenticated or no orders exist in the window.
  */
 async function getReportsSummary(
   brandId: string | null,