Speed up browser phone initialization

- Add preload hint for Twilio SDK to start loading earlier
- Add DNS prefetch and preconnect for Twilio servers
- Check SDK immediately instead of waiting 500ms
- Reduce polling interval from 100ms to 50ms

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

admin/class-twp-admin.php

@@ -7016,7 +7016,7 @@ class TWP_Admin {
                 <div class="phone-interface">
                     <div class="phone-display">
                         <div id="phone-status">Ready</div>
-                        <div id="device-connection-status" style="font-size: 12px; color: #999; margin-top: 5px;">Connecting...</div>
+                        <div id="device-connection-status" style="font-size: 12px; color: #999; margin-top: 5px;">Loading...</div>
                         <div id="phone-number-display"></div>
                         <div id="call-timer" style="display: none;">00:00</div>
                     </div>
@@ -7445,6 +7445,11 @@ class TWP_Admin {
             }
             </style>
             
+            <!-- Preload and preconnect for faster loading -->
+            <link rel="preload" href="https://unpkg.com/@twilio/voice-sdk@2.11.0/dist/twilio.min.js" as="script">
+            <link rel="dns-prefetch" href="//unpkg.com">
+            <link rel="dns-prefetch" href="//chunderw-vpc-gll.twilio.com">
+            <link rel="preconnect" href="https://chunderw-vpc-gll.twilio.com" crossorigin>
             <!-- Twilio Voice SDK v2 from unpkg CDN -->
             <script src="https://unpkg.com/@twilio/voice-sdk@2.11.0/dist/twilio.min.js"></script>
             <script>
@@ -8233,16 +8238,40 @@ class TWP_Admin {
                 });
                 
                 // Check if SDK loaded and initialize
-                $(window).on('load', function() {
+                // Poll for Twilio SDK availability (window.load may not fire on mobile)
-                    setTimeout(function() {
+                var sdkCheckAttempts = 0;
-                        if (typeof Twilio === 'undefined') {
+                var maxSdkCheckAttempts = 100; // 5 seconds max (100 * 50ms)
-                            showError('Twilio Voice SDK failed to load. Please check your internet connection and try refreshing the page.');
+
-                            console.error('Twilio SDK not found. Script may be blocked or failed to load.');
+                function checkAndInitialize() {
-                        } else {
+                    sdkCheckAttempts++;
+
+                    if (typeof Twilio !== 'undefined' && Twilio.Device) {
                         console.log('Twilio SDK loaded successfully');
                         initializeBrowserPhone();
+                    } else if (sdkCheckAttempts < maxSdkCheckAttempts) {
+                        // Keep checking every 50ms for faster response
+                        setTimeout(checkAndInitialize, 50);
+                    } else {
+                        showError('Twilio Voice SDK failed to load. Please check your internet connection and try refreshing the page.');
+                        console.error('Twilio SDK not found after ' + sdkCheckAttempts + ' attempts.');
+                    }
+                }
+
+                // Check immediately - SDK script is synchronous so should be loaded
+                // If not ready yet (mobile), polling will catch it
+                if (typeof Twilio !== 'undefined' && Twilio.Device) {
+                    console.log('Twilio SDK already loaded');
+                    initializeBrowserPhone();
+                } else {
+                    // Start polling immediately
+                    checkAndInitialize();
+                }
+
+                // Also keep the window.load as backup for desktop
+                $(window).on('load', function() {
+                    if (typeof Twilio !== 'undefined' && !device) {
+                        initializeBrowserPhone();
                     }
-                    }, 1000);
                 });
                 
                 // Clean up on page unload