…idebar_app_id (#19253)

This is a workaround for #18776

We avoid the foreign key issue by checking the previously inserted
workspace applications before calling UpdateWorkspaceAITask. Now,
affected workspaces will show as "not running an AI task" on the single
task view, which is technically correct.

We also insert a provisioner job log at WARN level to ensure that the
user sees some information that they have run into this issue, as well
as logging on the server side.

Longer term, we plan to modify how the workspace tasks view is
presented. This is a stopgap measure until we solidify that plan.

NOTE: this does **not** address the fact that stopping a workspace with
`has_ai_task: true` will result in the completed stop build no longer
having `has_ai_task: true`, resulting in tasks "disappearing" on stop.