PR plan pipelines were failing with "Error acquiring the state lock"
when they collided with a concurrent apply (or another plan) holding
the lock on the same Consul-backed state.
- plan: pass -lock=false to terragrunt plan; apply keeps locking
The generated backend.tf defines a terraform variable, so the Makefile
must export the API key as TF_VAR_prowlarr_api_key rather than PROWLARR_API_KEY.