Broaden app control plane to all workloads

[kacy]

Summary

• broaden the app-first control plane from service-only to include workers, crons, and training jobs
• extend remote workload control and app summaries to cover mixed-workload apps
• add clustered training log proxying through hosting agents and harden the log-read path

Highlights

• canonical app snapshots and release plans now carry services, workers, crons, and training jobs
• /apps/apply, app status/history/apps summaries, and remote worker/training commands now operate on the full workload model
• cluster cron schedules are registered from app apply state
• clustered training control tracks workload assignments, deduplicates summaries by job, and proxies rank logs through the hosting agent
• training log reads now reject invalid rank input and prefer local logs before remote proxy fallback

Validation

• ran targeted unit and route-flow coverage serially with YOQ_SKIP_SLOW_TESTS=1
• covered mixed-workload apply/rollback parity, worker and training route flows, cluster training assignment control, and clustered training log proxying