feat(api): dual-write Resource rows for new jobs and deploys

[eLRuLL]

Description

when a SpiderJob or Deploy is created through the existing serializers, optionally create a linked Resource row and set SpiderJob.resource / Deploy.resource.

• New helper module core/resource_dual_write.py with attach_spider_job_resource and attach_deploy_resource (idempotent, uses transaction.atomic + select_for_update).
• Wired from SpiderJobCreateSerializer.create (covers API job creation and launch_job) and DeployCreateSerializer.create.
• Gated by RESOURCE_DUAL_WRITE (default False via django-environ) so production is unchanged until explicitly enabled.
• Documented in .env.example.

Initial phase mapping: spider IN_QUEUE → PENDING, WAITING → PROVISIONING; deploy BUILDING → PROVISIONING. desired_spec holds minimal identifiers (jid / did).

No changes to Kubernetes dispatch, job lifecycle, or public API contracts.

Issue

• _N/A

Checklist before requesting a review

• I have performed a self-review of my code.
• My code follows the style guidelines of this project.
• I have made corresponding changes to the documentation. (.env.example only)
• New and existing tests pass locally with my changes.
• If this change is a core feature, I have added thorough tests. (optional; flag defaults off)
• If this change affects or depends on the behavior of other estela repositories, I have created pull requests with the relevant changes in the affected repositories. (not applicable)
• I understand that my pull request may be closed if it becomes obvious or I did not perform all of the steps above.