chore: gitignore secrets and add docker-compose override

Ignore .env and config/config.json to prevent committing secrets.
Add docker-compose.override.yml with resource limits.

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

.gitignore

@@ -44,3 +44,5 @@ tasks/
 
 # Added by goreleaser init:
 dist/
+.env
+config/config.json

docker-compose.override.yml

@@ -0,0 +1,10 @@
+# docker-compose.override.yml
+services:
+  picoclaw-agent:
+    deploy:
+      resources:
+        limits:
+          memory: 64M
+          cpus: '0.5'
+  picoclaw-gateway:
+    restart: unless-stopped