Use the new app icon

The icon now comes from images/mtga-assistant-icon.png: make_icon.py
copies it into the package (window, taskbar and tray icon) and builds
the Windows .ico used for the .exe. The old generated SVG icon is gone.
The PyInstaller spec also keeps QtNetwork, needed for single-instance.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packaging/mtga-assistant.spec

@@ -14,7 +14,6 @@ a = Analysis(
     # Qt modules the app doesn't use; keeps the bundle smaller.
     excludes=[
         "tkinter",
-        "PySide6.QtNetwork",
         "PySide6.QtQml",
         "PySide6.QtQuick",
         "PySide6.QtSql",
@@ -37,6 +36,6 @@ exe = EXE(
     exclude_binaries=True,
     name="MTGA Assistant",
     console=False,
-    icon=str(ROOT / "assets" / "icon.ico") if sys.platform == "win32" else None,
+    icon=str(ROOT / "images" / "mtga-assistant-icon.ico") if sys.platform == "win32" else None,
 )
 coll = COLLECT(exe, a.binaries, a.datas, name="MTGA Assistant")