When Gitea credentials are missing or the queue fetch fails closed,
show "Not loaded" instead of "No open items." and keep pagination
marked unavailable. Successful empty inventories still show the empty
state with complete pagination proof.
Closes#458
Adds read-only /queue and /api/queue routes that load open PRs and issues
from the default registry project via gitea_auth, surface pagination proof,
and classify items with claimed/blocked/in-review/duplicate badges.
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>