chore(supabase): full purge — remove all Supabase references from codebase

- Delete supabase/ directory (config.toml, push-migrations.js,
  ADMIN_CREATE_STOP_FIX.sql, 137 archived migration files)
- Remove @supabase/ssr and @supabase/supabase-js from package.json
- Strip *.supabase.co from next.config.ts image hostnames
- Strip https://*.supabase.co from vercel.json CSP connect-src
- Remove 'supabase/**' ignore from eslint.config.mjs
- Clean supabase references from src/lib/db.ts, vitest.config.ts,
  db/seeds/2026-tuxedo-tour-stops.sql, src/actions/storefront.ts,
  scripts/import-tuxedo-stops.ts comments
- Rewrite env-var docs in README, ENVIRONMENT, PRODUCTION_SETUP,
  PRODUCTION_DEPLOYMENT_CHECKLIST, LAUNCH_CHECKLIST, CLAUDE,
  MEMORY, REPORT to drop NEXT_PUBLIC_SUPABASE_URL /
  SUPABASE_SERVICE_ROLE_KEY / supabase link / supabase CLI references

The canonical migration runner is now scripts/migrate.js (uses pg
directly via DATABASE_URL). Migrations live in db/migrations/. The
Supabase CLI is no longer in the codebase. The only remaining
'@supabase/*' in the dep tree is @supabase/auth-js as a transitive
of @neondatabase/auth (Neon Auth / Better Auth).

Final source scan: grep -rln '@supabase\|rest/v1\|supabase\.co'
src/ tests/ db/ scripts/ next.config.ts vercel.json eslint.config.mjs
package.json returns zero. Verification: npm install clean
(11 added, 21 removed, 12 changed), tsc shows same 17 pre-existing
errors (Stripe dahlia API version + fetch preconnect mocks),
vitest 172/175 (3 pre-existing failures in getAdminUser.test.ts),
lint shows same 14 pre-existing errors. Live-tested: dev server
boots in 248ms, public storefronts (/) (/login) (/pricing) (/tuxedo)
(/indian-river-direct) all return 200; /admin/v2?demo=1 reaches 200
after dev_session redirect; storefront renders real brand content.

docs/water-log.md

@@ -180,7 +180,7 @@ data explicitly checks its gate.
   cold-start paths; the active `getAdminUser().brand_id` always wins
   on later requests.
 - No Supabase REST, no service-role keys — all access is direct
-  through Drizzle over a single `pg` Pool.
+  through Drizzle over a single shared `pg` Pool (see `src/lib/db.ts`).
 
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