Security: Extract API credentials to separate config file

- Move API credentials from script.js to config.js
- Add config.js to .gitignore to prevent credential exposure
- Create config.example.js as template for new installations
- Add validation check for missing configuration
- Update index.html to load config.js before script.js

This change ensures API keys are never committed to the repository
while maintaining full functionality of the dashboard.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

config.example.js

@@ -0,0 +1,6 @@
+// API Configuration Example
+// Copy this file to config.js and replace with your actual credentials
+const API_CONFIG = {
+    serverUrl: 'http://YOUR_UNRAID_IP:PORT/graphql',
+    apiKey: 'YOUR_API_KEY_HERE'
+};