app: open welcome page if clan doesn't exist

Previously if a user started the app and the last opened clan directory does not exist anymore, it would still show the clan screen but without any machines.

This changes catches this case and throws the user back to the clan selection page

pkgs/clan-cli/clan_cli/clan/show.py

@@ -15,7 +15,10 @@ log = logging.getLogger(__name__)
 
 
 @API.register
-def show_clan_meta(uri: str | Path) -> Meta:
+def show_clan_meta(uri: str) -> Meta:
+    if uri.startswith("/") and not Path(uri).exists():
+        msg = f"Path {uri} does not exist"
+        raise ClanError(msg, description="clan directory does not exist")
     cmd = nix_eval(
         [
             f"{uri}#clanInternals.inventory.meta",