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-sms-provider-twilio.php

@@ -0,0 +1,137 @@
+<?php
+/**
+ * Twilio SMS Provider
+ *
+ * SMS provider implementation for Twilio
+ */
+class TWP_SMS_Provider_Twilio implements TWP_SMS_Provider {
+
+    private $client;
+    private $default_from_number;
+
+    /**
+     * Constructor
+     */
+    public function __construct() {
+        $account_sid = get_option('twp_account_sid');
+        $auth_token = get_option('twp_auth_token');
+        $this->default_from_number = get_option('twp_sms_from_number');
+
+        if (!empty($account_sid) && !empty($auth_token)) {
+            $this->client = new Twilio\Rest\Client($account_sid, $auth_token);
+        }
+    }
+
+    /**
+     * Send an SMS message
+     *
+     * @param string $to_number Recipient phone number (E.164 format)
+     * @param string $message Message body
+     * @param string $from_number Sender phone number (E.164 format)
+     * @return array Response array with 'success' and 'data' or 'error'
+     */
+    public function send_sms($to_number, $message, $from_number = null) {
+        try {
+            if (!$this->client) {
+                return [
+                    'success' => false,
+                    'error' => 'Twilio client not initialized. Check API credentials.'
+                ];
+            }
+
+            // Determine the from number
+            $from = $from_number ?: $this->default_from_number;
+
+            // Validate we have a from number
+            if (empty($from)) {
+                error_log('TWP SMS Error: No from number available. Please configure SMS notification number in settings.');
+                return [
+                    'success' => false,
+                    'error' => 'No SMS from number configured. Please set SMS notification number in plugin settings.'
+                ];
+            }
+
+            $sms = $this->client->messages->create(
+                $to_number,
+                [
+                    'from' => $from,
+                    'body' => $message
+                ]
+            );
+
+            return [
+                'success' => true,
+                'provider' => 'twilio',
+                'data' => [
+                    'sid' => $sms->sid,
+                    'status' => $sms->status,
+                    'from' => $sms->from,
+                    'to' => $sms->to,
+                    'body' => $sms->body,
+                    'price' => $sms->price,
+                    'priceUnit' => $sms->priceUnit
+                ]
+            ];
+        } catch (\Twilio\Exceptions\TwilioException $e) {
+            return [
+                'success' => false,
+                'provider' => 'twilio',
+                'error' => $e->getMessage(),
+                'code' => $e->getCode()
+            ];
+        }
+    }
+
+    /**
+     * Get provider name
+     *
+     * @return string Provider name
+     */
+    public function get_provider_name() {
+        return 'Twilio';
+    }
+
+    /**
+     * Validate provider configuration
+     *
+     * @return array Response array with 'success' and 'message' or 'error'
+     */
+    public function validate_configuration() {
+        $account_sid = get_option('twp_account_sid');
+        $auth_token = get_option('twp_auth_token');
+        $from_number = get_option('twp_sms_from_number');
+
+        if (empty($account_sid)) {
+            return [
+                'success' => false,
+                'error' => 'Twilio Account SID is not configured'
+            ];
+        }
+
+        if (empty($auth_token)) {
+            return [
+                'success' => false,
+                'error' => 'Twilio Auth Token is not configured'
+            ];
+        }
+
+        if (empty($from_number)) {
+            return [
+                'success' => false,
+                'error' => 'SMS from number is not configured'
+            ];
+        }
+
+        if (!$this->client) {
+            return [
+                'success' => false,
+                'error' => 'Failed to initialize Twilio client'
+            ];
+        }
+
+        return [
+            'success' => true,
+            'message' => 'Twilio SMS provider is properly configured'
+        ];
+    }
+}