Fix broken application.app.controller references in Bluesky buffers

application.app was never set anywhere - application.py is just a
constants module. Every call to view_chat(), on_new_chat(),
view_conversation(), on_reposts(), and on_likes() crashed with
AttributeError, silently swallowed by get_event's except clause.

Fix: store controller reference on each buffer during create_buffer()
in mainController, then use self.controller instead of the broken
application.app.controller pattern throughout all Bluesky buffer and
dialog code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/controller/mainController.py

@@ -436,6 +436,7 @@ class Controller(object):
                 kwargs["parent"] = self.view.nb # self.view.nb is the wx.Treebook
 
             buffer = buffer_panel_class(**kwargs) # This is the wx.Panel instance
+            buffer.controller = self
 
             if start:
                 try: