Fix extrusion: catch ImportError on triangle and fallback to earcut

app.py

@@ -151,12 +151,12 @@ def create_3d_model(buildings: List[Dict]) -> trimesh.Scene:
             if debug: print(f"   ↳ skipping: polygon construction error: {e}")
             continue
         
-        # extrude
-        try:
+        # extrude: prefer triangle if available, otherwise earcut
             try:
                 extruded = trimesh.creation.extrude_polygon(polygon, height, engine="triangle")
-            except ValueError:
-                if debug: print("   ↳ triangle engine failed, trying earcut")
+            except (ImportError, ValueError) as e:
+                if debug:
+                    print(f"   ↳ triangle engine unavailable ({e}), falling back to earcut")
                 extruded = trimesh.creation.extrude_polygon(polygon, height, engine="earcut")
             
             if debug: