fix: switch to k8s-file log driver for reliable log capture

journald was dropping early startup logs. k8s-file writes directly
to disk, captures from process start, and is lighter on the Pi.
Capped at 10 MB with automatic rotation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -6,6 +6,10 @@ services:
     container_name: derp
     network_mode: host
     restart: unless-stopped
+    logging:
+      driver: k8s-file
+      options:
+        max_size: 10mb
     volumes:
       - ./src:/app/src:ro,Z
       - ./plugins:/app/plugins:ro,Z