Add zoom support to OxPage editor with 50% default

Toolbar zoom buttons (in/out/reset/fit) and Ctrl+MouseWheel now
control the page editor canvas when it is active. Frame image is
scaled via PIL for smooth rendering at any zoom level.

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

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.121"
+VERSION = "0.0.0.122"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True