Fix application icon not showing in PyInstaller builds

The icon wasn't working in frozen executables because:
1. LocalTranscription.png wasn't being bundled in the PyInstaller build
2. The code was using Path(__file__).parent which doesn't work in frozen exes

Changes:
- Added LocalTranscription.png to datas in local-transcription.spec
- Updated main.py to use sys._MEIPASS for frozen executables
- Updated gui/main_window_qt.py to use sys._MEIPASS for frozen executables
- Both files now detect if running frozen and adjust icon path accordingly

The icon will now appear correctly in:
- Window titlebar
- Taskbar (Windows) / Dock (macOS)
- Alt-Tab switcher

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

main.py

@@ -89,7 +89,14 @@ def main():
         app.setOrganizationName("LocalTranscription")
 
         # Set application icon
-        icon_path = project_root / "LocalTranscription.png"
+        # In PyInstaller frozen executables, use _MEIPASS for bundled files
+        if getattr(sys, 'frozen', False):
+            # Running in PyInstaller bundle
+            icon_path = Path(sys._MEIPASS) / "LocalTranscription.png"
+        else:
+            # Running in normal Python
+            icon_path = project_root / "LocalTranscription.png"
+
         if icon_path.exists():
             from PySide6.QtGui import QIcon
             app.setWindowIcon(QIcon(str(icon_path)))