Implement agent queue transfer functionality for browser phones

- Added ajax_get_transfer_agents endpoint to retrieve available agents
- Enhanced transfer system to support both phone numbers and personal queues
- Updated JavaScript transfer dialog to show agent selection with queue options
- Added personal queue database table creation for agent-to-agent transfers
- Implemented transfer-to-queue functionality using Twilio enqueue
- Added comprehensive CSS styling for new agent transfer dialog
- Each agent gets a personal queue (format: agent_{id}) for browser phone transfers
- Supports both phone transfers and browser phone queue transfers
- Enhanced UI shows transfer method options (phone vs browser phone queue)

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

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

assets/css/browser-phone-frontend.css

@@ -1138,4 +1138,119 @@
 @keyframes spin {
     0% { transform: rotate(0deg); }
     100% { transform: rotate(360deg); }
+}
+
+/* Agent Transfer Dialog Styles */
+.twp-agent-transfer-dialog {
+    max-width: 500px;
+    width: 90vw;
+}
+
+.agent-list {
+    max-height: 300px;
+    overflow-y: auto;
+    margin: 15px 0;
+    border: 1px solid #ddd;
+    border-radius: 6px;
+    background: #f9f9f9;
+}
+
+.agent-option {
+    padding: 12px;
+    border-bottom: 1px solid #eee;
+    background: white;
+    margin-bottom: 1px;
+}
+
+.agent-option:last-child {
+    border-bottom: none;
+}
+
+.agent-option.offline {
+    opacity: 0.6;
+    background: #f5f5f5;
+}
+
+.agent-info {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    margin-bottom: 8px;
+}
+
+.agent-name {
+    font-weight: 600;
+    font-size: 0.95rem;
+}
+
+.agent-status {
+    font-size: 0.85rem;
+    font-weight: 500;
+}
+
+.transfer-methods {
+    display: flex;
+    gap: 8px;
+    flex-wrap: wrap;
+}
+
+.transfer-option {
+    background: #e9ecef;
+    border: 2px solid #e9ecef;
+    padding: 6px 12px;
+    border-radius: 4px;
+    cursor: pointer;
+    font-size: 0.85rem;
+    transition: all 0.2s ease;
+    user-select: none;
+}
+
+.transfer-option:hover {
+    background: #dee2e6;
+    border-color: #adb5bd;
+}
+
+.transfer-option.selected {
+    background: #e3f2fd;
+    border-color: #2196f3;
+    color: #1976d2;
+}
+
+.transfer-option:active {
+    transform: scale(0.98);
+}
+
+.agent-option.offline .transfer-option {
+    opacity: 0.5;
+    cursor: not-allowed;
+}
+
+.agent-option.offline .transfer-option:hover {
+    background: #e9ecef;
+    border-color: #e9ecef;
+}
+
+.manual-option {
+    margin-top: 20px;
+    padding-top: 15px;
+    border-top: 1px solid #ddd;
+}
+
+.manual-option h4 {
+    margin: 0 0 8px 0;
+    font-size: 1rem;
+    color: #495057;
+}
+
+.manual-option p {
+    margin: 0 0 10px 0;
+    font-size: 0.9rem;
+    color: #6c757d;
+}
+
+.no-agents {
+    text-align: center;
+    padding: 20px;
+    color: #6c757d;
+    font-style: italic;
 }