Fix Cosmos container startup race during local Docker boot

[Chad Palmer (chadpalmer)]

Summary

• Fixes a local Docker startup failure where multiple gunicorn workers could race while creating first-run Cosmos containers.
• Adds conflict recovery around Cosmos create_container_if_not_exists so a worker re-reads and returns the container if another worker created it first.
• Adds focused regression coverage and fix documentation.
• Updates release notes under v0.250.062.

Validation

• git diff --check upstream/Development...HEAD
• python -m py_compile application/single_app/config.py functional_tests/test_cosmos_container_conflict_recovery.py
• python functional_tests/test_cosmos_container_conflict_recovery.py

Notes

• Branch was merged with latest upstream/Development.
• No route, UI, or browser-rendering files are changed in the final PR delta.
• Full Docker startup smoke test was not run locally as part of this validation, but local Docker instance did start up successfully after the updates.

[Chad Palmer (chadpalmer)]

Bionic711 Paul Lizer (@paullizer) This PR fixes a race condition for local docker instances where the gunicorn workers trip over each other in creating the first-run Cosmos containers.

[Paul Lizer (paullizer)]

I like this. Nice Chat! I also appreciated the other issues on UX and 508. Thank you!