Fix 2026.1 deprecations (#116)

Co-authored-by: Luke Morrigan <luke@lukeb.co.uk>

Author: joemcc-90

custom_components/robovac/vacuum.py

@@ -187,7 +187,7 @@ def ip_address(self) -> str | None:
         return self._attr_ip_address
 
     @property
-    def state(self) -> str | None:
+    def activity(self) -> str | None:
         if self.tuya_state is None:
             return STATE_UNAVAILABLE
         elif (