Add queue timeout voicemail and Amazon SNS SMS provider support

This update adds two major features:

1. Queue Timeout Voicemail
   - Callers can now leave voicemail when queue timeout is reached
   - Configurable per-queue voicemail prompts with TTS support
   - Automatic transcription and urgent keyword detection
   - Admin setting to choose between voicemail or callback on timeout

2. Amazon SNS SMS Provider
   - Alternative SMS provider to Twilio for sending text messages
   - Useful when Twilio SMS approval is difficult to obtain
   - Provider abstraction layer allows switching between Twilio/SNS
   - Full AWS SNS configuration in admin settings
   - Supports custom sender IDs in compatible countries
   - Lower cost per SMS compared to Twilio

New Files:
- includes/class-twp-voicemail-handler.php - Voicemail recording handler
- includes/interface-twp-sms-provider.php - SMS provider interface
- includes/class-twp-sms-provider-twilio.php - Twilio SMS implementation
- includes/class-twp-sms-provider-sns.php - Amazon SNS implementation
- includes/class-twp-sms-manager.php - SMS provider abstraction manager
- QUEUE_VOICEMAIL_SMS_FEATURES.md - Complete feature documentation

Modified Files:
- includes/class-twp-call-queue.php - Added voicemail option to timeout handler
- includes/class-twp-twilio-api.php - Updated send_sms() to use provider abstraction
- admin/class-twp-admin.php - Added SMS provider and timeout action settings
- composer.json - Added AWS SDK dependency

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

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

includes/class-twp-call-queue.php

@@ -168,7 +168,7 @@ class TWP_Call_Queue {
     private function handle_timeout($call, $queue) {
         global $wpdb;
         $table_name = $wpdb->prefix . 'twp_queued_calls';
-        
+
         // Update status
         $wpdb->update(
             $table_name,
@@ -180,15 +180,36 @@ class TWP_Call_Queue {
             array('%s', '%s'),
             array('%d')
         );
-        
-        // Offer callback instead of hanging up
-        $callback_twiml = TWP_Callback_Manager::create_callback_twiml($queue->id, $call->from_number);
-        
+
+        // Get timeout action preference (default to voicemail)
+        $timeout_action = get_option('twp_queue_timeout_action', 'voicemail');
+
         $twilio = new TWP_Twilio_API();
-        $twilio->update_call($call->call_sid, array(
-            'twiml' => $callback_twiml
-        ));
-        
+
+        if ($timeout_action === 'voicemail') {
+            // Offer voicemail recording
+            require_once dirname(__FILE__) . '/class-twp-voicemail-handler.php';
+            $voicemail_twiml = TWP_Voicemail_Handler::create_voicemail_twiml(
+                $call->from_number,
+                $queue->id
+            );
+
+            $twilio->update_call($call->call_sid, array(
+                'twiml' => $voicemail_twiml
+            ));
+
+            error_log("TWP Queue Timeout: Directing call {$call->call_sid} to voicemail");
+        } else {
+            // Offer callback (original behavior)
+            $callback_twiml = TWP_Callback_Manager::create_callback_twiml($queue->id, $call->from_number);
+
+            $twilio->update_call($call->call_sid, array(
+                'twiml' => $callback_twiml
+            ));
+
+            error_log("TWP Queue Timeout: Offering callback to {$call->from_number}");
+        }
+
         // Reorder queue
         self::reorder_queue($queue->id);
     }