fix(relay): route China deploys through mirrors

[bobleer]

Summary

• propagate the resolved Auto/China/Global route through Docker installation, detached deployment, the published-binary runtime image, and source-build fallback
• pass the China apt mirror into the generated runtime Dockerfile while retaining the trixie glibc compatibility floor
• add a wizard override for inaccurate cloud IP geolocation, route-reason logging, bounded apt retries/timeouts, documentation, and regression coverage

Root cause

The Docker daemon registry mirror accelerated the base-image pull, but the generated published-binary Dockerfile still ran apt inside the image against deb.debian.org. Host apt settings cannot affect that build step, so a correctly detected mainland-China host could still stall or fail.

Verification

• cargo test -p bitfun-services-integrations --features remote-ssh,remote-ssh-concrete relay_deploy --lib (32 passed)
• cargo check --workspace
• pnpm run type-check:web
• pnpm run lint:web
• pnpm run i18n:audit
• bash -n src/apps/relay-server/{mirror.sh,release-download.sh,deploy.sh}
• git diff --check

Live Docker image building was not available locally because the Docker daemon is not running; the build-argument path is covered by a shell-backed regression test.