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_recipe_routes.py

@@ -210,6 +210,49 @@ class TestDxfCompareProxy:
         mock_api_client.post.assert_not_called()
 
 
+class TestDxfPreviewProxy:
+    """#101: anteprima del DXF scelto nel wizard (proxy verso il backend)."""
+    URL = "/maker/api/vision/dxf-preview"
+    OK = {
+        "contorni": [[[0.0, -5.0], [10.0, -5.0], [10.0, 0.0], [0.0, 0.0]]],
+        "bbox": {"xmin": 0.0, "ymin": -5.0, "xmax": 10.0, "ymax": 0.0},
+        "larghezza_mm": 10.0, "altezza_mm": 5.0, "entita": 1, "punti": 4,
+    }
+
+    def _post(self, client, with_file=True):
+        data = {"dxf": (io.BytesIO(b"0\nEOF"), "d.dxf")} if with_file else {}
+        return client.post(self.URL, data=data, content_type="multipart/form-data")
+
+    def test_forwards_file(self, logged_in_client, mock_api_client):
+        mock_api_client.post.return_value = self.OK
+        resp = self._post(logged_in_client)
+        assert resp.status_code == 200
+        assert resp.get_json()["larghezza_mm"] == 10.0
+        args, kwargs = mock_api_client.post.call_args
+        assert args[0] == "/api/vision/dxf-preview"
+        assert set(kwargs["files"]) == {"dxf"}
+        assert kwargs["files"]["dxf"][0] == "d.dxf"
+        assert kwargs["files"]["dxf"][1] == b"0\nEOF"
+
+    def test_missing_file_is_400(self, logged_in_client, mock_api_client):
+        resp = self._post(logged_in_client, with_file=False)
+        assert resp.status_code == 400
+        mock_api_client.post.assert_not_called()
+
+    def test_backend_422_propagates(self, logged_in_client, mock_api_client):
+        mock_api_client.post.return_value = {
+            "error": True, "status_code": 422, "detail": "DXF illeggibile: x"}
+        resp = self._post(logged_in_client)
+        assert resp.status_code == 422
+        assert resp.get_json()["detail"] == "DXF illeggibile: x"
+
+    def test_requires_maker_role(self, logged_in_client, mock_api_client):
+        with logged_in_client.session_transaction() as sess:
+            sess["user"] = {**sess["user"], "roles": ["MeasurementTec"]}
+        assert self._post(logged_in_client).status_code == 403
+        mock_api_client.post.assert_not_called()
+
+
 class TestPages:
     def test_stations_page_has_calibration_cell(self, logged_in_client):
         with patch("blueprints.admin.api_client") as admin_api:
@@ -236,4 +279,5 @@ class TestPages:
         assert "dxfRecipeWizard(" in html
         assert "@dxf-recipe-saved" in html
         assert 'x-model="mmPx"' in html  # #98: campo mm/px a mano
+        assert "dxfPreviewPaths()" in html  # #101: anteprima SVG del DXF
         assert "Pezzo scuro su fondo chiaro" in html or "Dark part on light" in html