chore: sync gtfs-realtime.proto from upstream and regenerate bindings

[github-actions]

Automated proto sync

The upstream gtfs-realtime.proto
changed. This PR syncs it into the repo and regenerates every
language binding via codegen/generate.sh.

Before merging

• Approve the Bindings CI run on this PR. GitHub does not
  auto-run workflows on PRs opened by GITHUB_TOKEN, so the
  checks start as "action required" until a maintainer approves.
• Review the proto diff for breaking vs. additive changes.
• Bump the affected per-language package versions.
• Confirm the Bindings CI checks pass.

Generated by the proto-sync workflow.