[Feature] Notifications/Transfer Event Support

[therangerangler]

Summary

Add support for publishing transfer events to AWS SNS and/or SQS, allowing File Mover Express to integrate with other services and workflows when transfers complete, fail, or encounter errors.

Background

File Mover Express already has an internal event bus (src/cli/events/bus.go) that fires well-defined events throughout the transfer lifecycle — job created, job complete, job error, task complete, and more. Today these events are consumed internally by the GUI and logged. They are not exposed externally.

Adding SNS/SQS as an optional event destination would allow users to:

• Trigger downstream workflows when a transfer job completes (e.g. kick off a transcoding pipeline)
• Alert on transfer failures via email, SMS, or PagerDuty through SNS subscriptions
• Feed transfer events into other services via SQS consumers
• Build audit trails of transfer activity without polling

Existing events available to publish

The following events are already defined and carry useful data:

• JobCompleteEvent — job ID, name, completion time, whether any tasks errored or were skipped
• JobErrorEvent — job ID, name, error time, error message
• TaskCompleteEvent — task ID, direction (upload/download), destination path
• JobCreateEvent — fired when a new job is queued
• JobProgressEvent — periodic progress updates

Proposed approach

Add an optional notification configuration block to the config file:

notifications:
  sns:
    enabled: true
    topic_arn: "arn:aws:sns:us-east-1:123456789:my-topic"
    events:
      - job_complete
      - job_error
  sqs:
    enabled: false
    queue_url: "https://sqs.us-east-1.amazonaws.com/123456789/my-queue"
    events:
      - job_complete
      - job_error
      - task_complete

On startup, if notifications are configured, register a new listener on the existing event bus. When a matching event fires, publish it to the configured SNS topic or SQS queue as a JSON payload.

The existing AWS credentials (profile/region from the transfer profile) should be reused for SNS/SQS access.

Implementation notes

• The event bus already supports RegisterListener with event type filters — a notification publisher would just be another listener
• Each event type already implements String() and carries structured data, making JSON serialisation straightforward
• SNS and SQS both use the AWS SDK v2 which is already a dependency
• IAM permissions for sns:Publish or sqs:SendMessage would need to be added to the setup documentation

Relevant files

• src/cli/events/bus.go — event bus, RegisterListener is the integration point
• src/cli/types/eventtypes/ — all event type definitions
• src/cli/types/configtypes/config.go — where the new notifications config block would be added
• docs/Configuration.md — would need updating with the new config options
• docs/Setup.md — would need the additional IAM permissions documented

Acceptance criteria

• SNS and/or SQS publishing can be enabled via configuration
• Users can choose which event types trigger a notification
• Notifications are non-blocking — a failure to publish should log a warning but not affect the transfer
• Credentials use the existing AWS profile configuration
• Documentation updated for configuration and required IAM permissions