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/Dockerfile

@@ -18,7 +18,8 @@ RUN pnpm exec turbo run build --filter=@sauci/shared
 
 # Build admin app with env vars
 ARG VITE_SUPABASE_URL
-ARG VITE_SUPABASE_ANON_KEY
+ARG VITE_SUPABASE_ANON_KEY
+ARG VITE_API_URL
 ARG VITE_OPENAI_API_KEY
 ARG VITE_OPENROUTER_API_KEY
 ARG VITE_AI_MODEL
@@ -30,7 +31,8 @@ ARG VITE_COUNCIL_GENERATOR_MODEL
 ARG VITE_COUNCIL_REVIEWER_MODEL
 
 ENV VITE_SUPABASE_URL=$VITE_SUPABASE_URL
-ENV VITE_SUPABASE_ANON_KEY=$VITE_SUPABASE_ANON_KEY
+ENV VITE_SUPABASE_ANON_KEY=$VITE_SUPABASE_ANON_KEY
+ENV VITE_API_URL=$VITE_API_URL
 ENV VITE_OPENAI_API_KEY=$VITE_OPENAI_API_KEY
 ENV VITE_OPENROUTER_API_KEY=$VITE_OPENROUTER_API_KEY
 ENV VITE_AI_MODEL=$VITE_AI_MODEL