Added filesystem-based secrets loading configuration

examples/pipeline.minimal.yml

@@ -4,6 +4,11 @@ workspace:
 storage:
   backend: local
 
+secrets:
+  # Optional: load environment variables from files in this directory.
+  # File name = env var name; file contents = env var value.
+  env_dir: /var/local/narratio/secrets
+
 whisperx:
   transcribe_url: "https://transcription.example.com/transcribe"
   language: "en"