fix: remove @frenchfryai/runtime to eliminate suspected memory leak

[jerelvelarde]

Summary

• Removes @frenchfryai/runtime dependency and the /realtime/session route registration
• The realtime session route is unused by this demo and is the most likely source of the monotonic heap growth causing OOM crashes (WebSocket/SSE sessions that disconnect uncleanly may leave references in a session registry)
• Per Tyler: "Realtime session isn't needed, we can remove that"

Test plan

• Deploy and monitor heap usage — if the leak was in frenchfry, heap should stabilize instead of growing monotonically
• Verify /api/copilotkit still works normally
• Confirm no more exit-134 OOM crashes in Render logs

[jerelvelarde]

Clean, surgical removal — only touches what's necessary.

What looks good:

• Minimal change scoped to exactly the unused dependency and its route registration
• Clear rationale linking the unclean WebSocket/SSE disconnects to the monotonic heap growth
• Test plan targets the actual concern (heap stabilization, OOM crash elimination)

Worth revisiting after deploy:

• The resilience.js import sits right after the removed block. If that module was added specifically to work around the frenchfry leak, it may also be removable once heap usage stabilizes.
• The blank line left between app.route(...) and the // Error resilience comment is cosmetic but could be tightened.