Accept the Lao desktop layout from the setup form (#257)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

configs/airootfs/usr/share/omarchy-iso/orchestrator/keyboard.py

@@ -71,5 +71,5 @@ def configure_keyboard(target: Path, language: str, input_method: str | None = N
 def validate_input_selection(input_method: str | None, xkb_layout: str) -> None:
     if input_method is not None and input_method not in {"none", "mozc", "hangul", "pinyin", "chewing"}:
         raise ValueError(f"Unknown input method: {input_method}")
-    if xkb_layout not in {"", "kr"}:
+    if xkb_layout not in {"", "kr", "la"}:
         raise ValueError(f"Unknown input keyboard layout: {xkb_layout}")