Migrate ActiveJob adapter from delayed_job to Sidekiq

[Copilot]

Replaces delayed_job with Sidekiq for background job processing. Sidekiq provides better performance through Redis-backed queuing versus database-backed queuing, and is actively maintained.

Core Changes

• Dependencies: Replace delayed_job_active_record with sidekiq (~> 7.0) and redis (~> 5.0)
• Configuration: Update ActiveJob adapter to :sidekiq, create Sidekiq initializer with Redis connection and queue configuration matching previous delayed_job setup (single retry, 24-hour timeout)
• Worker Management: Rewrite lib/seek/workers.rb to manage Sidekiq processes while preserving existing rake task interface (seek:workers:start/stop/restart/status)
• Admin Controller: Update clear_failed_jobs to use Sidekiq API (Sidekiq::DeadSet, Sidekiq::RetrySet) instead of ActiveRecord queries

Infrastructure

• Docker: Add Redis service to all docker-compose configurations with REDIS_URL environment variable
• Migration: Drop unused delayed_jobs table (irreversible)
• Logging: Switch from delayed_job logs to log/sidekiq.log

Backward Compatibility

Rake tasks and admin interface unchanged. Added delayed_job_pids alias in Seek::Util to maintain compatibility with existing code that checks worker status.

Migration Path

Requires Redis running (localhost:6379 or REDIS_URL env var). See MIGRATION_NOTES_SIDEKIQ.md for installation steps and troubleshooting.

# Queue configuration preserved
QueueNames::DEFAULT = 'default'.freeze  # Previously Delayed::Worker.default_queue_name
QueueNames::MAILERS = 'mailers'.freeze  # Unchanged

# Worker management API unchanged
Seek::Workers.start    # Now starts Sidekiq instead of delayed_job
Seek::Workers.stop     # Graceful shutdown with 10s timeout

Original prompt

Migrate the ActiveJob adapter from delayed_job to sidekiq

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