added basic connection between the files, fixed small issues. some parts were achieved using ai.

main.py

@@ -6,3 +6,90 @@ haTerm is a Terminal Based hafas client, using the ivb endpoint.
 Prompt_toolkit (https://github.com/prompt-toolkit/python-prompt-toolkit) will be used to render a terminal user interface (TUI).
 The application will provide routing information and station departures/arrivals.
 """
+
+from backend import HafasClient
+import route_planning
+import station_monitor
+
+from prompt_toolkit import Application
+from prompt_toolkit.layout import Layout, HSplit, VSplit, Window
+from prompt_toolkit.widgets import Button, Box
+from prompt_toolkit.key_binding import KeyBindings
+
+
+def pk_menu(client: HafasClient):
+	"""Display a centered menu with two buttons selectable by arrow keys.
+
+	The function runs a full-screen prompt_toolkit application. Left/right
+	arrows move focus between the buttons; Enter activates the focused
+	button. The function returns the chosen mode as a string or None when
+	the user quits.
+	"""
+	choice = {'value': None}
+
+	def on_rp():
+		choice['value'] = 'rp'
+		app.exit()
+
+	def on_sm():
+		choice['value'] = 'sm'
+		app.exit()
+
+	btn_rp = Button("Route Planning", handler=on_rp, width=20)
+	btn_sm = Button("Station Monitor", handler=on_sm, width=20)
+
+	buttons = [btn_rp, btn_sm]
+	index = {'i': 0}
+
+	kb = KeyBindings()
+
+	def focus_current():
+		app.layout.focus(buttons[index['i']])
+
+	@kb.add('left')
+	def _left(event):
+		index['i'] = max(0, index['i'] - 1)
+		focus_current()
+
+	@kb.add('right')
+	def _right(event):
+		index['i'] = min(len(buttons) - 1, index['i'] + 1)
+		focus_current()
+
+	@kb.add('q')
+	@kb.add('c-q')
+	@kb.add('c-c')
+	def _quit(event):
+		app.exit()
+
+	root = HSplit(children=[
+		Window(),
+		Box(VSplit(children=[
+			Window(),
+			Box(VSplit(children=buttons, padding=6), padding=2, style="bg:#2A71D5 fg:#FFFFFF"),
+			Window()
+        ])),
+        Window()
+	], align='CENTER')
+
+	app = Application(layout=Layout(root, focused_element=btn_rp), key_bindings=kb, full_screen=True)
+	app.run()
+	return choice['value']
+
+
+def main():
+	client = HafasClient()
+
+	while True:
+		result = pk_menu(client)
+		if result == 'rp':
+			route_planning.run_route_planning(client)
+		elif result == 'sm':
+			station_monitor.run_station_monitor(client)
+		else:
+			print("Exiting.")
+			break
+
+
+if __name__ == '__main__':
+	main()