fix: strip plugin timers when pickling Host to prevent save failure

Host.plugin_timers holds asyncio TimerHandle objects (and their lambda
callbacks) which are not picklable, causing the 5-minute state save to
fail with "Can't pickle local object reset_plugin_timer.<locals>.<lambda>".
Add Host.__getstate__ to reset plugin_timers to {} before pickling,
mirroring Connection.__getstate__; timers are recreated on the next PLG.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

hbd/server/hbdclass.py

@@ -304,6 +304,14 @@ class Host:
         self.managers: list = []            # usernames with manager role
         self.monitors: list = []            # usernames with monitor role
 
+    def __getstate__(self):
+        """Prepare Host for pickling by excluding non-serializable timer objects."""
+        state = self.__dict__.copy()
+        # asyncio TimerHandles (and their lambda callbacks) can't be pickled.
+        # They're recreated when the next PLG arrives after unpickling.
+        state['plugin_timers'] = {}
+        return state
+
     def statedict(self):
         d = {}
         d["raw_name"] = self.name