docs: update CLAUDE.md with config file usage

CLAUDE.md

@@ -33,4 +33,23 @@ uv run pytest
 
 ## Configuration
 
-Credentials can be passed via command-line options (`-u/--url`, `-U/--username`, `-P/--password`) or environment variables (`JENKINS_URL`, `JENKINS_USERNAME`, `JENKINS_PASSWORD` or `JENKINS_TOKEN`).
+Credentials are read from `~/.config/zzpyjenkins/config.toml`. Create this file with your Jenkins server configurations:
+
+```toml
+[work]
+url = "https://jenkins.work.com"
+username = "myuser"
+password = "mypassword"
+
+[home]
+url = "http://localhost:8080"
+username = "admin"
+password = "admin123"
+```
+
+Use `-s/--server` option to select which server to use:
+
+```bash
+zzpyjenkins -s work info
+zzpyjenkins --server home list
+```