Simplify script injection to single script with data attribute configuration

- Replace dual script injection (external + inline) with single script approach
- Pass site configuration via data attributes instead of inline JavaScript
- Update library auto-initialization to read config from script data attributes
- Reduce HTML bloat by eliminating 30+ lines of inline initialization code
- Maintain future-proof CDN compatibility and duplication prevention

Enhanced files now contain only one clean script tag with configuration.

lib/src/index.js

@@ -79,7 +79,18 @@ window.Insertr = {
 // Auto-initialize in development mode with proper DOM ready handling
 function autoInitialize() {
     if (document.querySelector('.insertr')) {
-        window.Insertr.init();
+        // Check for configuration from script data attributes
+        const insertrScript = document.querySelector('script[data-insertr-injected]');
+        const config = {};
+        
+        if (insertrScript) {
+            config.siteId = insertrScript.getAttribute('data-site-id') || 'demo';
+            config.apiEndpoint = insertrScript.getAttribute('data-api-endpoint') || '/api/content';
+            config.mockAuth = insertrScript.getAttribute('data-mock-auth') === 'true';
+            config.debug = insertrScript.getAttribute('data-debug') === 'true';
+        }
+        
+        window.Insertr.init(config);
     }
 }