feat: ship redacted tinycloud-node logs to Better Stack - #288

Ship tinycloud-node logs to Better Stack via a Vector sidecar (GELF/UDP), with a field allowlist and per-line size cap.

• Vector service, config and tests under log-shipper/
• Compose: logging driver and labels, Vector service
• Node: JSON log line cap
• Acceptance harness and helper scripts
• CI: schema and packaging checks

Tests: vector test, node --test, Rust unit tests, acceptance harness.

Tracking: TC-959