Azure App Service Linux: persistent storage error blocks Kudu ZIP deployment and new web app provisioning

Question

I have an existing Linux/Python 3.12 App Service in France Central on a Basic B1 plan.

A GitHub Actions deployment uses the documented Kudu ZIP Deploy endpoint. The full test suite passes, but every deployment returns HTTP 409. I performed one controlled restart and one retry; no parallel deployments are running.

To determine whether the failure was deployment-specific, I tried to provision an empty Linux/Python 3.12 web app in the existing B1 plan. Provisioning fails with:

Storage access failed. Storage access failure - please retry later. Please delete and recreate backup schedule to mitigate.

The Backups blade shows automatic hourly backups but zero backup results. The existing instance's latest startup classification includes a local SQLite "file is not a database" error, but the platform storage error prevents deployment of an already-tested recovery fix.

What self-service Azure App Service steps can safely restore platform storage / Kudu deployment state? I must preserve existing /home application data and cannot reset it. I do not want to delete or recreate the existing app.