Have SaveRaceJob inherit from ActiveJob::Base and remove ApplicationJob

[maxmetcalfe]

Motivation

• Fix a production eager-load failure caused by relying on a missing ApplicationJob base class.
• Ensure race-saving work runs asynchronously so controller requests do not block.
• Keep the UI responsive by setting race state to FINISHED immediately before background processing.
• Provide a simple in-process job backend for background execution.

Description

• Deleted the unused app/jobs/application_job.rb base class and updated SaveRaceJob to inherit from ActiveJob::Base in app/jobs/save_race_job.rb.
• Enqueued background work with SaveRaceJob.perform_later(race.id) and set the race state to FINISHED before redirecting in RacesController#save_race.
• Added config.active_job.queue_adapter = :async to config/application.rb to enable an in-process job adapter for simple background execution.
• SaveRaceJob computes race_count, fav_bib, and updates streak calendars for affected Racer records in the background.

Testing

• No automated tests were run for these changes.
• Manual verification steps were not recorded as part of this PR.

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Codex Task