Improve visibility of processing service status in UI

[annavik]

Summary

• Show if a processing service is online or offline
• Show where results are coming from in job logs

Based on request from @mihow related to processing v2.

[annavik]

@mihow I think you fixed most of this, right?

[mihow]

Claude says: Online/offline status (#1146) and per-task worker logging (#1238) are merged. The remaining async per-service "Unknown" status is covered by the in-flight API-key identity work, PR #1194 / #1201. Linking for tracking.