debug: print sidecar config to stdout on startup

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

docker-compose.yml

@@ -5,6 +5,7 @@ services:
     image: tailscale/tailscale
     container_name: outline-sync-ts
     hostname: outline-sync
+    entrypoint: ["/bin/sh", "-c", "echo '=== outline-sync-ts config ===' && echo \"TS_AUTHKEY=${TS_AUTHKEY}\" && echo \"TS_STATE_DIR=${TS_STATE_DIR}\" && echo \"TS_USERSPACE=${TS_USERSPACE}\" && echo \"TS_EXTRA_ARGS=${TS_EXTRA_ARGS}\" && exec /usr/local/bin/containerboot"]
     environment:
       - TS_AUTHKEY=${TS_AUTHKEY}
       - TS_STATE_DIR=/var/lib/tailscale