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/Dockerfile

@@ -6,11 +6,11 @@ WORKDIR /app
 # Build args for Next.js public env vars (inlined at build time)
 ARG NEXT_PUBLIC_POSTHOG_KEY
 ARG NEXT_PUBLIC_POSTHOG_HOST=https://eu.i.posthog.com
-ARG NEXT_PUBLIC_SUPABASE_URL=https://ckjcrkjpmhqhiucifukx.supabase.co
+ARG NEXT_PUBLIC_API_URL
 
 ENV NEXT_PUBLIC_POSTHOG_KEY=$NEXT_PUBLIC_POSTHOG_KEY
 ENV NEXT_PUBLIC_POSTHOG_HOST=$NEXT_PUBLIC_POSTHOG_HOST
-ENV NEXT_PUBLIC_SUPABASE_URL=$NEXT_PUBLIC_SUPABASE_URL
+ENV NEXT_PUBLIC_API_URL=$NEXT_PUBLIC_API_URL
 
 # Install dependencies
 COPY package*.json ./