check if openscad is installed on system

seedling_tray.py

@@ -5,7 +5,7 @@ import subprocess
 import sys
 from pathlib import Path
 
-from utils import ask_int, ask_float
+from utils import ask_int, ask_float, check_openscad
 
 
 BASE_DIR = Path(__file__).resolve().parent
@@ -54,6 +54,8 @@ def render_scad(
 
 
 def main() -> None:
+    check_openscad()
+
     if not SCAD_DIR.exists():
         raise SystemExit(f"Missing SCAD directory: {SCAD_DIR}")