Disable votes on votes

Added check to prevent voting on bot/group messages (UIDs < 0).
This prevents users from voting on karma change messages posted by the bot.

Fixes #18

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: konard

python/modules/commands.py

@@ -170,6 +170,10 @@ def apply_karma(self) -> NoReturn:
             if selected_user_id:
                 self.user = self.data_service.get_user(int(selected_user_id), self)
 
+        # Disable votes on bot messages (votes on votes)
+        if self.user and self.user.uid < 0:
+            return
+
         if self.user and (self.user.uid != self.from_id):
             operator = self.matched.group("operator")[0]
             amount = self.matched.group("amount")