chore(build): update application icon

Convert images/icon.jpg to build/icon.ico for Windows executable.
The new icon is a 1264x848 pixel image converted to multi-resolution ICO format.

Changes:
- Add images/icon.jpg (source icon)
- Update build/icon.ico (converted for PyInstaller)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: codewizdave