Add command-line options for Jenkins credentials

Allow passing URL, username, and password via global options (-u, -U, -P)
as an alternative to environment variables. Options take precedence over
environment variables.

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

README.md

@@ -25,7 +25,15 @@ uv run zzpyjenkins --help
 
 ## Configuration
 
-Set the following environment variables:
+You can provide Jenkins credentials via command-line options or environment variables:
+
+### Command-line options (preferred)
+
+```bash
+zzpyjenkins -u https://jenkins.example.com -U username -P token info
+```
+
+### Environment variables
 
 ```bash
 export JENKINS_URL="https://your-jenkins-server.com"