Route SP check jobs to workers by SP region (multi-region routing)

## Summary

Once dealbot is deployed multi-region (per [FilOzone/infra#69](https://github.com/FilOzone/infra/pull/69) — workers in nbg1, ash, sin), all worker pods will pull from the same pg-boss queue. Without job routing by SP region, an APAC SP's job can still be picked up by an EU worker, so the multi-region deployment alone does **not** fix APAC reachability failures.

## Background

Investigation in #478 showed APAC SPs (e.g. ruka-main, superusey-calib) fail dealbot checks from the current single-region (nbg1) egress due to long-haul TCP/TLS issues, not SP-side bugs. Tippy confirmed those SPs are healthy from APAC clients.

[FilOzone/infra#69](https://github.com/FilOzone/infra/pull/69) adds worker pods in 3 regions and a \`region\` metric label, but does **not** introduce any routing layer. Job-to-worker assignment remains \"random\" via shared queue.

## Acceptance criteria

- [ ] Provider config carries a region tag (e.g. \`spRegion: 'EU' | 'NA' | 'APAC'\`) — manual tagging is acceptable initially
- [ ] Jobs for an SP are dispatched to a queue scoped to that SP's region
- [ ] Each worker pod subscribes only to the queue matching its own deployment region (env var driven)
- [ ] Jobs for SPs without a region tag fall back to a default queue / region (probably EU)
- [ ] \`dataSetCreationStatus\` and other check metrics, broken down by \`region\` label, show APAC SPs succeeding when handled by sin worker
- [ ] Documented runbook for adding new regions or moving SPs between regions

## Suggested approach (lightest)

1. Add \`spRegion\` to provider model / config.
2. In \`apps/backend/src/jobs/jobs.service.ts\`, when enqueuing a job for an SP, derive queue name from SP region (e.g. \`sp-jobs-eu\`, \`sp-jobs-na\`, \`sp-jobs-apac\`).
3. Worker subscribes to a single queue selected via \`DEALBOT_REGION\` env var injected by the deployment (already varies per region in the infra PR).
4. Default-route untagged SPs to the EU queue to preserve current behavior.

## Out of scope

- Auto-detecting SP region from chain-registered metadata (could be future work — start manual)
- Queue rebalancing across regions when one is down (start with strict region routing; revisit if it becomes a reliability problem)

## Related

- Infra PR: [FilOzone/infra#69](https://github.com/FilOzone/infra/pull/69) (multi-region worker deployment, prerequisite)
- Investigation: #478 (APAC reachability failures, includes SP-by-SP failure verification)