feat: per-queue job browser

[eclectic-coding]

Summary

• Per-queue job browser — queue names and sizes on the Queues index are now links to GET /queues/:id, which shows a paginated list of ready jobs for that queue with individual Discard buttons and a "Discard All Ready (N)" header action; pause/resume controls are present on the show page so operators never need to leave the queue context
• Refactor: pause/resume → Queues::PausesController#create/destroy — replaced non-standard pause/resume member actions with a nested singular resource (resource :pause), giving standard CRUD action names and a consistent URL (/queues/:queue_id/pause for both verbs); redirect_back_or_to keeps the user on the show page when toggling from there
• Refactor: set_ids before_action in FailedJobs::SelectionsController — eliminated the duplicated ids assignment across create and destroy

Test plan

• Visit /queues — queue names and sizes are links
• Click a queue name — lands on /queues/:id showing only that queue's ready jobs
• Discard a single job from the queue show page — job disappears; redirects to filtered jobs list
• "Discard All Ready" — confirms and removes all ready jobs for that queue
• Pause/resume from the queue show page — badge updates; stays in queue context
• Pause/resume from the queues index — still works
• bundle exec rake passes (159 examples, 0 failures)

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