Kiosk binary now forwards all tracing logs to Axiom when
BF_AXIOM_KEY + BF_AXIOM_DATASET are set at compile time via
option_env!(). Batches up to 50 entries or flushes every 10s.
No-op when keys not baked in (local dev builds).
CI build.yml passes secrets as env vars for cargo build.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
