Fix/18 auto continue on usage reset

[irmorteza]

Summary

• add quota_monitor.go: background daemon tracks quotaReached flag and probes the provider every 15 minutes to detect when quota has reset
• block workers via waitIfQuotaReached() when quota is hit and resume automatically
• re-queue jobs on ErrTokensExhausted instead of marking them failed
• add ProbeProvider() to Orchestrator for lightweight LLM ping
• add FlowStatusRescheduled status for tickets waiting on quota reset
• add rescheduled to OpenAPI schema for future WebUI support

Testing

• go test ./...
• set provider to bash -c 'echo "usage limit reached" >&2; exit 1' and run a ticket
• observe ticket status changes to rescheduled and job re-queues automatically
• after 20 minutes observe quota monitor probes and resumes workers

~/.auto-pr/config.yaml

provider: fake-exhausted

providers:
  fake-exhausted:
    command: bash
    args:
      - -c
      - 'echo "usage limit reached" >&2; exit 1'

Notes

• system jobs (cleanup) blocked during quota pause will be addressed in a follow-up issue

Known Limitations

when a ticket is waiting for quota reset, all workers are paused including system jobs (cleanup, cleanup-all). this will be fixed in a follow-up issue by splitting the job queue into llmJobs and systemJobs channels with dedicated worker pools.