fix(auth): revert SUPABASE_INTERNAL_URL — cookie name mismatch

Browser creates cookies keyed by the external hostname (sb-myeasycms-*),
but server was using SUPABASE_INTERNAL_URL (sb-supabase-kong-*) — different
keys = server can't find the session = infinite 'please wait' after login.

Both client and server now use the same NEXT_PUBLIC_SUPABASE_URL (external
domain). The SSR reaches Supabase via Traefik → Kong which works fine.

Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /app
 # --- Install + Build in one stage ---
 FROM base AS builder
 # CACHE_BUST: change this value to force a full rebuild (busts Docker layer cache)
-ARG CACHE_BUST=9
+ARG CACHE_BUST=10
 RUN echo "Cache bust: ${CACHE_BUST}"
 COPY . .
 RUN pnpm install --no-frozen-lockfile