[2.x] feat: pausable queues

[imorland]

Implements the queue pause/resume surface that QueueFactory has stubbed since #4673/#4683, removing the TODO. Works across all queue backends — database, redis, and Horizon workers all consult this same factory when popping jobs.

How it works

Illuminate's Worker filters paused queues in getNextJob() via the manager's pause surface. QueueFactory now answers for real, backed by the shared cache store with Illuminate's exact key format (illuminate:queue:paused:{connection}:{queue}) — so the signal reaches every worker process, across containers, and interoperates with anything speaking the upstream convention. QueuePaused/QueueResumed events are dispatched for parity.

• Per-queue + wildcard: pause($conn, 'media') or pause($conn, '*') — the wildcard covers every queue on the connection, so pause-all needs no queue enumeration (core can't portably enumerate queue names across backends). The layers are orthogonal: resume-all doesn't clear individually paused queues.
• pausedQueues($connection) — a Flarum addition tracking what's paused, self-healing when pauseFor() TTLs expire or pauses are cleared externally. Powers the dashboard warning.
• queue:pause / queue:resume — Flarum-native commands (the stock Illuminate ones type-hint the concrete QueueManager). Accept queue or connection:queue, default to the active connection, support --all. Registered only for non-sync connections.
• POST /api/queue/pause — admin-gated; refuses with 409 on the sync driver (inline execution, nothing to pause).
• flarum.queue.queues container binding — queue names known to the installation (default ['default']); extensions routing jobs via AbstractJob::$onQueue append theirs to get per-queue admin controls.

Admin UI

• Dashboard: non-dismissible warning whenever any queue is paused (wording distinguishes "all" from named queues), with a Manage link — same pattern as the maintenance-mode alert.
• Advanced page: with one known queue, a single "Pause queue processing" switch (wired to the wildcard); with several, a pause-all switch plus per-queue switches. No controls on sync.

Validation

• 17 integration tests: factory semantics (cache key format, wildcard, orthogonality, self-healing list, events), worker pop behaviour on the database driver, command registration/behaviour, endpoint auth/sync-refusal. Full suite 743 green, PHPStan clean.
• Live-verified on a Horizon deployment: while paused, a pushed job sat in redis; after queue:resume it drained within seconds — commands issued from the web container, workers running in a separate container.

Operator note

Long-running workers evaluate pause state with the code they booted with — a one-time queue:restart after upgrading picks up the new factory.

Follow-ups (fof/horizon)

Register supervisor queue names into flarum.queue.queues; supervisor-profile extender with grouped pause controls; cross-container horizon:pause/continue.