Add comprehensive call control features and web phone transfer capabilities

## New Call Control Features
- Call hold/unhold with music playback
- Call transfer with agent selection dialog
- Call requeue to different queues
- Call recording with start/stop controls
- Real-time recording status tracking

## Enhanced Transfer System
- Transfer to agents with cell phones (direct)
- Transfer to web phone agents via personal queues
- Automatic queue creation for each user
- Real-time agent availability status
- Visual agent selection with status indicators (📱 phone, 💻 web)

## Call Recordings Management
- New database table for call recordings
- Recordings tab in voicemail interface
- Play/download recordings functionality
- Admin-only delete capability
- Integration with Twilio recording webhooks

## Agent Queue System
- Personal queues (agent_[user_id]) for web phone transfers
- Automatic polling for incoming transfers
- Transfer notifications with browser alerts
- Agent status tracking (available/busy/offline)

## Technical Enhancements
- 8 new AJAX endpoints for call controls
- Recording status webhooks
- Enhanced transfer dialogs with agent selection
- Improved error handling and user feedback
- Mobile-responsive call control interface

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

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

includes/class-twp-shortcodes.php

@@ -171,6 +171,24 @@ class TWP_Shortcodes {
                 </div>
             </div>
             
+            <!-- Call Control Panel (shown during active calls) -->
+            <div class="twp-call-controls-panel" id="twp-call-controls-panel" style="display: none;">
+                <div class="call-control-buttons">
+                    <button id="twp-hold-btn" class="twp-btn twp-btn-control" title="Put call on hold">
+                        Hold
+                    </button>
+                    <button id="twp-transfer-btn" class="twp-btn twp-btn-control" title="Transfer to another agent">
+                        Transfer
+                    </button>
+                    <button id="twp-requeue-btn" class="twp-btn twp-btn-control" title="Put call back in queue">
+                        Requeue
+                    </button>
+                    <button id="twp-record-btn" class="twp-btn twp-btn-control" title="Start/stop recording">
+                        Record
+                    </button>
+                </div>
+            </div>
+            
             <!-- Queue Management Section -->
             <div class="twp-queue-section" id="twp-queue-section">
                 <h4>Your Queues</h4>