feat(backend): add standalone data plane

Replace the Supabase application data plane with the Node/PostgreSQL API, migrate mobile, admin, web, and MCP callers, add controlled cutover tooling, and define hardened Dokploy infrastructure.

apps/admin/.env.example

@@ -1,5 +1,8 @@
-VITE_SUPABASE_URL=your_supabase_url
-VITE_SUPABASE_ANON_KEY=your_supabase_anon_key
+# Hosted Supabase Auth public settings only. Admin product data and mutations go
+# through VITE_API_URL; never expose a service-role or admin service token here.
+VITE_SUPABASE_URL=your_nonproduction_supabase_auth_url
+VITE_SUPABASE_ANON_KEY=your_nonproduction_supabase_anon_key
+VITE_API_URL=http://127.0.0.1:3003
 VITE_OPENAI_API_KEY=your_openai_api_key
 VITE_OPENROUTER_API_KEY=your_openrouter_api_key