Fix browser phone Twilio SDK loading and CSS layout issues

- Update Twilio SDK URL from sdk.twilio.com to unpkg CDN (same as backend)
- Change SDK version from 2.11.1 to 2.11.0 for consistency
- Fix dial number input overflow by adding box-sizing: border-box
- Ensure all elements use border-box sizing model

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

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

includes/class-twp-shortcodes.php

@@ -26,12 +26,12 @@ class TWP_Shortcodes {
         global $post;
         
         if (is_a($post, 'WP_Post') && has_shortcode($post->post_content, 'twp_browser_phone')) {
-            // Enqueue Twilio Voice SDK with multiple fallbacks
+            // Enqueue Twilio Voice SDK from unpkg CDN (same as backend)
             wp_enqueue_script(
                 'twilio-voice-sdk',
-                'https://sdk.twilio.com/js/voice/2.11.1/twilio.min.js',
+                'https://unpkg.com/@twilio/voice-sdk@2.11.0/dist/twilio.min.js',
                 array(),
-                '2.11.1',
+                '2.11.0',
                 false // Load in head to ensure it's available
             );
             
@@ -41,7 +41,7 @@ class TWP_Shortcodes {
                     if (typeof Twilio === 'undefined') {
                         console.warn('Primary Twilio SDK failed, attempting fallback load');
                         var script = document.createElement('script');
-                        script.src = 'https://sdk.twilio.com/js/voice/2.11.1/twilio.min.js';
+                        script.src = 'https://unpkg.com/@twilio/voice-sdk@2.11.0/dist/twilio.min.js';
                         script.onload = function() { console.log('Fallback Twilio SDK loaded'); };
                         script.onerror = function() { console.error('Fallback Twilio SDK failed'); };
                         document.head.appendChild(script);