Fix hold button to properly show Resume state when call is on hold

- Enhanced Call SID detection using multiple fallback methods
- Fixed button state logic to properly toggle between Hold/Resume
- Added immediate UI feedback during hold operations
- Enhanced error handling with proper button state reversion
- Added distinctive orange styling for active hold button state
- Improved user messaging to clarify when call is on hold
- Added comprehensive console logging for debugging hold operations
- Fixed logic error in button state updates

The button will now properly show:
- "Hold" when call is active (normal state)
- "Resume" when call is on hold (orange/active state)
- Loading states during operations ("Holding..." / "Resuming...")

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

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

assets/css/browser-phone-frontend.css

@@ -1253,4 +1253,17 @@
     padding: 20px;
     color: #6c757d;
     font-style: italic;
+}
+
+/* Hold button active state */
+.twp-btn.btn-active {
+    background-color: #ff6b35 !important;
+    color: white !important;
+    border-color: #e55100 !important;
+    font-weight: bold;
+}
+
+.twp-btn.btn-active:hover {
+    background-color: #e55100 !important;
+    border-color: #bf360c !important;
 }