Defer GUI launcher imports so individual tabs work without webrtc extra

gui/__init__.py used to eagerly import main_window, which transitively
loaded RemoteDesktopTab → webrtc_panel → webrtc_transport, requiring
the optional 'webrtc' extra (PyAV / aiortc). That broke any caller
doing 'from je_auto_control.gui.<tab> import X' on environments that
only installed the base wheel. Move the launcher imports inside
start_autocontrol_gui() so importing a single tab no longer pulls in
the WebRTC stack.

Author: JE-Chen

je_auto_control/gui/__init__.py

@@ -1,11 +1,22 @@
-import sys
+"""GUI package — kept import-light so individual tabs can be loaded without
+pulling in the full main window (which transitively requires the optional
+``webrtc`` extra). The launcher imports its dependencies lazily inside
+:func:`start_autocontrol_gui` so::
 
-from PySide6.QtWidgets import QApplication
+    from je_auto_control.gui.profiler_tab import ProfilerTab
 
-from je_auto_control.gui.main_window import AutoControlGUIUI
+works in environments that have not installed PyAV / aiortc.
+"""
 
 
-def start_autocontrol_gui():
+def start_autocontrol_gui() -> None:
+    """Open the AutoControl GUI; pulls in PySide6 + WebRTC stack lazily."""
+    import sys
+
+    from PySide6.QtWidgets import QApplication
+
+    from je_auto_control.gui.main_window import AutoControlGUIUI
+
     app = QApplication(sys.argv)
     window = AutoControlGUIUI()
     window.show()