Add custom icon and tray-minimize behavior (like VersaGUI's TrayApp)

Minimizing or closing hides the window instead of leaving a taskbar
entry; only "Beenden" in the tray right-click menu really exits. Tray
callbacks route through a queue instead of touching Tk directly from
pystray's thread (same pattern as the earlier serial-thread fix).

Also fixes the build script: PyInstaller failed on the network share
while copying Tcl/Tk tzdata (path-length issue), so building now
happens in a local temp copy instead of directly on Z:.

Adds an info button that explains the MCP server's available tools.

VersaPadViewer.spec

@@ -5,7 +5,7 @@ a = Analysis(
     ['desktop_viewer.py'],
     pathex=[],
     binaries=[],
-    datas=[],
+    datas=[('icon.png', '.'), ('icon.ico', '.')],
     hiddenimports=[],
     hookspath=[],
     hooksconfig={},
@@ -32,6 +32,7 @@ exe = EXE(
     target_arch=None,
     codesign_identity=None,
     entitlements_file=None,
+    icon=['icon.ico'],
 )
 coll = COLLECT(
     exe,