feat: add named durable job queues and worker observability

[joaovitoriasilva]

What does this PR do?

Adds named durable-job queues, selective and fair workers, and durable worker observability while preserving the existing default queue behavior.

Key changes:

• Assign queues when durable subscribers register, then stamp each queue during outbox fan-out.
• Support all-queue and explicit non-empty queue allowlists with fair rotation across selected queues.
• Add the public blocking run_job_worker() entry point for standalone PostgreSQL workers.
• Keep SQLite limited to one API process with one in-process consumer.
• Add restart-unique worker identities, independent heartbeats, graceful-stop tracking, active-claim counts, status derivation, and bounded retention.
• Expose queue and worker summaries through jasil.admin.
• Add rolling-safe packaged migrations with a database-side default queue value.
• Add real PostgreSQL competing-consumer and worker-observability conformance tests.

Related issue

No related issue was provided. This work was requested and implemented directly.

Type of change

Check all that apply

• Bug fix
• New feature (exception during freeze; link prior discussion/acknowledgment)
• Documentation
• Refactor / code quality
• Translation
• Other (describe below)

Checklist

• This PR is focused on a single concern
• An issue was opened and acknowledged before writing this code (if not a small fix)
• If this PR introduces a new feature during freeze, it was discussed and explicitly acknowledged first
• The PR is under ~300 lines changed, excluding lock files, migrations, and generated code
• Tests have been added or updated where applicable
• Documentation has been updated where applicable
• Commit messages follow Conventional Commits format

Notes for the reviewer

Design decisions:

• Queue ownership belongs to subscriber registration because one event can fan out to subscribers on different queues.
• JASIL owns neutral worker identity and telemetry persistence. The host continues to own routes, authentication, authorization, UI, alerts, and health policy.
• Durable jobs remain database-backed and do not require Redis.

Validation completed:

• SQLite: 1,023 passed, 7 skipped, 98.21% coverage.
• PostgreSQL 17: 1,028 passed, 2 skipped, 98.13% coverage.
• MySQL 8.4 compatibility slice: 165 passed, 3 skipped.
• Ruff, format, strict mypy, five import contracts, strict MkDocs, API reference validation, wheel smoke testing, and strict Twine checks passed.
• The built wheel contains all three migration revisions and maps all four JASIL tables with base dependencies only.