Add database-backed job queue with WP-Cron and loopback workers

[ahamed]

Adds a Laravel-style queue for plugins built on the framework, designed for WordPress hosting where no queue:work daemon can run.

Job API

• ShouldQueue contract and Queueable trait; a job is a class with handle(), whose class-typed parameters are resolved from the container.
• Job::dispatch(...) returns a pending dispatch written on destruction, with delay(), on_queue() and with_priority(); plus dispatch_if, dispatch_unless and dispatch_sync.
• Inside handle(): attempts(), release($delay) and fail($e).
• $tries, $backoff (seconds or per-attempt array) and failed(Throwable).

Storage and processing

• Jobs live in app-prefixed {prefix}jobs / {prefix}failed_jobs tables, so several framework plugins on one site never share a queue.
• Workers claim batches atomically with a single tokened UPDATE ... ORDER BY priority DESC ... LIMIT n, work within a time budget, hand back unstarted jobs without using an attempt, and reclaim reservations older than retry_after so a crashed worker cannot strand a job.
• An every-minute WP-Cron sweep and a shutdown spawn after undelayed dispatches start an HMAC-signed, non-blocking admin-ajax loopback worker that daisy-chains until the queue is empty. One chain runs at a time.

Opt-in and tooling

• Enabled only by registering QueueServiceProvider; without it nothing is hooked and dispatch throws a helpful QueueException.
• Queue facade (push, later, size, clear) and Queue::fake() with assert_pushed, assert_pushed_times, assert_not_pushed, assert_nothing_pushed.
• JobQueued, JobProcessing, JobProcessed, JobFailed events; failures are also logged.
• WP-CLI: queue:table (generates migrations, runs no DDL), make:job, queue:work, queue:failed, queue:retry, queue:forget, queue:flush, queue:clear.
• docs/queues.md, including the blocked-loopback / low-traffic fallback and where this differs from Laravel; optional config/queue.php in the example.

Also records the grilling preference in CLAUDE.md.

New public API is tagged @SInCE 3.2.0.