Fix UI spacing and reset detected FPS label

Add gap=15 to the index/backend row in the camera settings form to improve spacing, and ensure the detected FPS label is reset to '—' when clearing camera configuration values so the UI consistently shows cleared state.

Author: C-Achard

dlclivegui/gui/camera_config_dialog.py

@@ -466,7 +466,7 @@ def _setup_ui(self) -> None:
         self.cam_backend_label = QLabel("opencv")
         # self.settings_form.addRow("Backend:", self.cam_backend_label)
         id_backend_row = _make_two_field_row(
-            "Index:", self.cam_index_label, "Backend:", self.cam_backend_label, key_width=120
+            "Index:", self.cam_index_label, "Backend:", self.cam_backend_label, key_width=120, gap=15
         )
         self.settings_form.addRow(id_backend_row)
 
@@ -1124,6 +1124,7 @@ def _clear_settings_form(self) -> None:
         self.cam_index_label.setText("")
         self.cam_backend_label.setText("")
         self.detected_resolution_label.setText("—")
+        self.detected_fps_label.setText("—")
         self.cam_width.setValue(0)
         self.cam_height.setValue(0)
         self.cam_fps.setValue(0.0)