Fix SDK timeout and improve text contrast

SDK Loading Improvements:
- Increased timeout from 5 to 15 seconds for slower connections
- Added progressive status messages during SDK loading
- Enhanced console logging for debugging
- Added fallback SDK loading mechanism with inline script
- Better error diagnostics showing Twilio object status

Text Contrast Fixes:
- Updated all #333 colors to #212529 for better readability
- Fixed browser phone title, dial buttons, timer, queue headings
- Enhanced dark mode support for all text elements
- Improved readability on both light and dark backgrounds

Technical Changes:
- waitForTwilioSDK() now waits 150 attempts (15 seconds)
- Progressive status updates at 3s, 6s, 10s intervals
- Backup SDK loading via document.createElement
- Comprehensive dark mode color coverage
- Better error messaging for network issues

Accessibility Improvements:
- Higher contrast ratios for WCAG compliance
- Consistent text color hierarchy
- Better visibility in all lighting conditions
- Enhanced mobile readability

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

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

includes/class-twp-shortcodes.php

@@ -26,7 +26,7 @@ class TWP_Shortcodes {
         global $post;
         
         if (is_a($post, 'WP_Post') && has_shortcode($post->post_content, 'twp_browser_phone')) {
-            // Enqueue Twilio Voice SDK
+            // Enqueue Twilio Voice SDK with multiple fallbacks
             wp_enqueue_script(
                 'twilio-voice-sdk',
                 'https://sdk.twilio.com/js/voice/2.11.1/twilio.min.js',
@@ -35,6 +35,23 @@ class TWP_Shortcodes {
                 false // Load in head to ensure it's available
             );
             
+            // Add backup SDK loading
+            wp_add_inline_script('twilio-voice-sdk', "
+                window.twpLoadTwilioSDK = function() {
+                    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.onload = function() { console.log('Fallback Twilio SDK loaded'); };
+                        script.onerror = function() { console.error('Fallback Twilio SDK failed'); };
+                        document.head.appendChild(script);
+                    }
+                };
+                
+                // Try loading after a delay if not available
+                setTimeout(window.twpLoadTwilioSDK, 2000);
+            ", 'after');
+            
             // Enqueue our browser phone script
             wp_enqueue_script(
                 'twp-browser-phone-frontend',