Suppress login bind point message and auto-join Local channel

Only show "Your home has been set" when the player actively changes their
bind point (via innkeeper), not on the initial login sync from the server.
Add "Local" to the auto-join channel list for Turtle WoW compatibility,
with a settings checkbox and persistence.

include/ui/game_screen.hpp

@@ -231,6 +231,7 @@ private:
     bool chatAutoJoinTrade_ = true;
     bool chatAutoJoinLocalDefense_ = true;
     bool chatAutoJoinLFG_ = true;
+    bool chatAutoJoinLocal_ = true;
 
     // Join channel input buffer
     char joinChannelBuffer_[128] = "";