Phil/agent jwt secret

[psFried]

Description:

Updates the agent to read CONTROL_PLANE_JWT_SECRET from the env instead of querying it from the database. Supabase recently did a rug pull on app.settings.jwt_secret, and agents were relying on the presence of that as part of their startup routine. This updates agent to read the jwt secret from an env variable instead of querying it from the database.

Also updates the internal.access_token_jwt_secret sql function to read the jwt secret from vault instead of relying on app.settings.jwt_secret.

I also hacked in a disablement of the periodic publications, since the fix to make those apply to tasks only hasn't merged yet.

The migration has already been run, and the agents have already been deployed.

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This change is 

[jshearer]

LGTM