Fix song/application access: property not method call

ControlSurface exposes song and application as properties, not callable
methods. Replace manager.song() and manager.application() with the correct
attribute access throughout handler, application, browser, and view modules.

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

AbletonOSC/application.py

@@ -17,7 +17,7 @@ class ApplicationHandler(AbletonOSCHandler):
 
     def _app(self):
         try:
-            return self.manager.application()
+            return self.manager.application
         except Exception:
             return None