Add smoke e2e workflow

[michaelw]

Summary

• add make smoke / test-e2e for ephemeral kind cluster validation
• add Debian smoke workflow gated by the smoke PR label and nightly/manual triggers
• add Linux host DNS and root CA diagnostics while keeping normal DevSpace operations shell-only

Validation

• go test ./tests/e2e/...
• go test -count=1 -run '^$' ./tests/install
• GOOS=linux go test -c -o /tmp/devspace-starter-pack-install-linux.test ./tests/install
• make test
• git diff --check