harden delivery pipeline and production runtime

app/ha/client.py

@@ -31,10 +31,13 @@ class HaClient:
             "Content-Type": "application/json",
         })
 
+    def close(self) -> None:
+        self._session.close()
+
     def list_entities(self) -> list[dict[str, object]]:
         try:
             response = self._session.get(
-                f"{self._settings.url}/api/states",
+                f"{self._settings.url.rstrip('/')}/api/states",
                 timeout=self._settings.timeout_seconds,
             )
         except requests.Timeout as exc:
@@ -71,4 +74,4 @@ class HaClient:
                 "Antwort von Home Assistant hat unerwartetes Format."
             )
 
-        return payload
+        return payload