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/web/docker-compose.prod.yml

@@ -8,7 +8,7 @@ services:
       args:
         - NEXT_PUBLIC_POSTHOG_KEY=${NEXT_PUBLIC_POSTHOG_KEY}
         - NEXT_PUBLIC_POSTHOG_HOST=${NEXT_PUBLIC_POSTHOG_HOST:-https://eu.i.posthog.com}
-        - NEXT_PUBLIC_SUPABASE_URL=${NEXT_PUBLIC_SUPABASE_URL:-https://ckjcrkjpmhqhiucifukx.supabase.co}
+        - NEXT_PUBLIC_API_URL=${NEXT_PUBLIC_API_URL:?NEXT_PUBLIC_API_URL is required}
     environment:
       - NODE_ENV=production
       - NEXT_TELEMETRY_DISABLED=1