Add EmailQueueService with Redis dispatch for async email jobs

Description

 EmailQueueService that persists email jobs to the email_jobs table and notifies the background worker via Redis.

• Added EmailQueueService with enqueueMailerAction() to:
  • create a pending row in email_jobs
  • JSON-encode the payload
  • push the job ID to Redis queue cdli:queue:email
  • register the queue in cdli:queues
• Added App\Service\QueueKeys with shared Redis queue constants/helpers used by EmailQueueService and TaskComponent:
  • QUEUE_REGISTRY_KEY
  • QUEUE_KEY_PREFIX
  • queueKey()
• Added unit tests for:
  • DB write path
  • Redis push path
  • Redis failure handling (job remains pending in DB)