web UI added and refactoring done

python_app/webui/__init__.py

@@ -0,0 +1,15 @@
+"""Isolated, Qt-free web frontend for the radar_system Pi appliance.
+
+The web UI streams the live GPR view and exposes the pipeline controls of the
+desktop app without any Qt dependency. It depends only on the small
+:class:`~python_app.webui.controller.WebController` contract; the embedded Qt
+bridge (``gui/controllers/app_window_web_mixin.py``) implements that contract by
+forwarding to the AppWindow's existing buttons, so no control flow is duplicated.
+
+- :mod:`controller` — the Qt-free control/read contract.
+- :mod:`streaming` — latest-wins fan-out of plot frames/status/settings to clients.
+- :mod:`routes` / :mod:`app` — FastAPI surface and application factory.
+- :mod:`server` — run the app on a background thread inside the host process.
+"""
+
+from __future__ import annotations