Fix extension transfer system and browser phone compatibility

Major Fixes:
- Fixed extension transfers going directly to voicemail for available agents
- Resolved browser phone call disconnections during transfers
- Fixed voicemail transcription placeholder text issue
- Added Firefox compatibility with automatic media permissions

Extension Transfer Improvements:
- Changed from active client dialing to proper queue-based system
- Fixed client name generation consistency (user_login vs display_name)
- Added 2-minute timeout with automatic voicemail fallback
- Enhanced agent availability detection for browser phone users

Browser Phone Enhancements:
- Added automatic microphone/speaker permission requests
- Improved Firefox compatibility with explicit getUserMedia calls
- Fixed client naming consistency across capability tokens and call acceptance
- Added comprehensive error handling for permission denials

Database & System Updates:
- Added auto_busy_at column for automatic agent status reversion
- Implemented 1-minute auto-revert system for busy agents with cron job
- Updated database version to 1.6.2 for automatic migration
- Fixed voicemail user_id association for extension voicemails

Call Statistics & Logging:
- Fixed browser phone calls not appearing in agent statistics
- Enhanced call logging with proper agent_id association in JSON format
- Improved customer number detection for complex call topologies
- Added comprehensive debugging for call leg detection

Voicemail & Transcription:
- Replaced placeholder transcription with real Twilio API integration
- Added manual transcription request capability for existing voicemails
- Enhanced voicemail callback handling with user_id support
- Fixed transcription webhook processing for extension voicemails

Technical Improvements:
- Standardized client name generation across all components
- Added ElevenLabs TTS integration to agent connection messages
- Enhanced error handling and logging throughout transfer system
- Fixed TwiML generation syntax errors in dial() methods

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

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

includes/class-twp-callback-manager.php

@@ -111,7 +111,7 @@ class TWP_Callback_Manager {
             );
             
             // Set agent to busy
-            TWP_Agent_Manager::set_agent_status($agent->user_id, 'busy', $agent_call_result['call_sid']);
+            TWP_Agent_Manager::set_agent_status($agent->user_id, 'busy', $agent_call_result['call_sid'], true);
             
             return true;
         }
@@ -206,7 +206,7 @@ class TWP_Callback_Manager {
         
         if ($agent_call_result['success']) {
             // Set agent to busy
-            TWP_Agent_Manager::set_agent_status($agent_user_id, 'busy', $agent_call_result['call_sid']);
+            TWP_Agent_Manager::set_agent_status($agent_user_id, 'busy', $agent_call_result['call_sid'], true);
             
             // Log the outbound call
             TWP_Call_Logger::log_call(array(