fix(launcher): set TCL_LIBRARY/TK_LIBRARY for embedded Python

Embedded Python ships with tcl8.6/ and tk8.6/ next to python.exe, but
Tcl's auto-detection searches <exe>/../lib/tcl8.6 — a path that doesn't
exist in our layout. Without these env vars, tkinter.Tk() raises
"Can't find a usable init.tcl", breaking the screen overlay (and any
other tk-based UI) on installed builds.

server/src/wled_controller/__main__.py

@@ -13,12 +13,33 @@ import time
 import webbrowser
 from pathlib import Path
 
-import uvicorn
 
-from wled_controller.config import get_config
-from wled_controller.server_ref import set_server, set_tray
-from wled_controller.tray import PYSTRAY_AVAILABLE, TrayManager
-from wled_controller.utils import setup_logging, get_logger
+def _fix_embedded_tcl_paths() -> None:
+    """Point TCL_LIBRARY/TK_LIBRARY at the bundled tcl/tk dirs.
+
+    The Windows installer ships embedded Python with tcl8.6/ and tk8.6/
+    next to python.exe, but Tcl's auto-detection searches ``<exe>/../lib/tcl8.6``
+    and similar paths that don't exist in our layout. Without these env vars,
+    ``tkinter.Tk()`` fails with "Can't find a usable init.tcl", which breaks
+    both the screen overlay and tray messageboxes.
+    """
+    exe_dir = Path(sys.executable).parent
+    tcl_dir = exe_dir / "tcl8.6"
+    tk_dir = exe_dir / "tk8.6"
+    if (tcl_dir / "init.tcl").is_file():
+        os.environ.setdefault("TCL_LIBRARY", str(tcl_dir))
+    if (tk_dir / "tk.tcl").is_file():
+        os.environ.setdefault("TK_LIBRARY", str(tk_dir))
+
+
+_fix_embedded_tcl_paths()
+
+import uvicorn  # noqa: E402
+
+from wled_controller.config import get_config  # noqa: E402
+from wled_controller.server_ref import set_server, set_tray  # noqa: E402
+from wled_controller.tray import PYSTRAY_AVAILABLE, TrayManager  # noqa: E402
+from wled_controller.utils import setup_logging, get_logger  # noqa: E402
 
 setup_logging()
 logger = get_logger(__name__)