The Release Web workflow builds the Docker image with the repo root as
context (file: ./apps/web/infra/Containerfile), but the Containerfile's
ADD/COPY still referenced ./packages/web/dist and
./packages/web/infra/default.conf. After #1097 moved the web app to
apps/web, those paths no longer exist, so buildx failed with
'"/packages/web/infra/default.conf": not found'.
Point both at ./apps/web/. Verified with a local multi-stage docker
build against the apps/web build output.
