maker: anteprima del DXF nel wizard «Crea ricetta da DXF» (Refs #101)

Proxy Flask /maker/api/vision/dxf-preview (piano B), stato e funzioni
dxfPreview* nel wizard, riquadro SVG con L x H sotto il campo .dxf,
traduzioni e test (proxy, JS con node, pagina).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/frontend/flask_app/tests/test_dxf_preview_js.py

@@ -0,0 +1,35 @@
+"""Runs the plain-node DXF preview behaviour test (tests/js/test_dxf_preview.js).
+
+Same thin pytest wrapper pattern as test_numpad_js.py: shells out to ``node``
+and asserts the script's own exit code. Skips (does not fail) when node is
+not installed.
+
+Covers gitea:Adriano/TieMeasureFlow#101.
+"""
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+FLASK_APP_DIR = Path(__file__).resolve().parent.parent
+JS_TEST = Path(__file__).resolve().parent / "js" / "test_dxf_preview.js"
+
+
+def test_dxf_preview_js_behaviour():
+    node = shutil.which("node")
+    if not node:
+        pytest.skip("node non installato: test JS di dxf_recipe_wizard.js saltato")
+
+    result = subprocess.run(
+        [node, str(JS_TEST)],
+        cwd=str(FLASK_APP_DIR),
+        capture_output=True,
+        text=True,
+        timeout=30,
+    )
+
+    assert result.returncode == 0, (
+        f"tests/js/test_dxf_preview.js fallito (exit {result.returncode})\n"
+        f"stdout:\n{result.stdout}\nstderr:\n{result.stderr}"
+    )