fix: wildcard drvPath tolerance, fair-share idle gate, all-scores Live Jobs (#419)

[DerDennisOP]

Fixes #419 (three parts), and bundles two local fixes (#427, #428).
Fixes #427
Fixes #428

#419

• Wildcard drvPath: an attr matched only by a */# wildcard that has no .drvPath is skipped silently; only an attr the user pinpointed exactly still surfaces the resolution error.
• FairShareRule: the penalty now applies only when every worker is busy, so a lone busy org is never pushed below the dispatcher's zero floor into leaving the cluster idle.
• Live Jobs all scores: the scheduler keeps a bounded ring of recent dispatch decisions with every candidate's score (incl. rejected/negative), exposed at GET /board/jobs/decisions (superuser) and shown via a new "dispatched / incl. rejected" dropdown.

Bundled

• project url parse error #427: strip the flake git+ scheme before libgit2 repo polling.
• Sending Gitea test web hook fails with 400 #428: accept all-zero-SHA push webhooks (deletion / test ping) as a 200 no-op.