feat: live image polling on ODLC Images page

[Michael-R-Dickinson]

Summary

• Adds an Auto-refresh toggle to the ODLC Images page that polls for new images every second and merges them into the session without reloading existing ones
• Introduces a lightweight sidecar index file ({session_id}.index.json) per session containing only [{id, receivedAt}] — the poll hot path reads this tiny file instead of the full multi-MB session JSON, keeping CPU load flat as sessions grow
• Adds GET /vision/odlc-session/{id}/index/?since=<ms> and GET /vision/odlc-session/{id}/records/{record_id}/ endpoints; renames patch_odlc_record → odlc_record to reflect it now handles both GET and PATCH

Test plan

• Toggle Auto-refresh on — verify new images received via WebRTC appear in the list within ~1 second without clearing existing images or annotations
• Toggle Auto-refresh off — verify polling stops (no further network requests to the index endpoint)
• Navigate away from the ODLC Images page with Auto-refresh on — verify the interval is cleared (no background requests)
• With a large existing session, confirm the poll on "nothing new" only hits the index endpoint (small response), not the full session file
• Annotate or flag an image while Auto-refresh is on — verify the annotation is not overwritten by an incoming poll
• Confirm existing session restore on page load still works correctly

Written by michael 👨

[maplesyrup-0606]

I assume this is an attempt to reduce the upload speed? If so, how much was reduced, was that measured?

[Michael-R-Dickinson]

I assume this is an attempt to reduce the upload speed? If so, how much was reduced, was that measured?

On the macbook we got < 2s from capture button to image showing up on another tab, but this probably isn't representative of how it will perform on the mercpad. We'll test more soon