Fix filter by scale counters and add consist constrains

Still to be improved, see FIXME

ram/consist/migrations/0017_consist_scale.py

@@ -0,0 +1,42 @@
+# Generated by Django 5.1.4 on 2025-05-01 09:51
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+def set_scale(apps, schema_editor):
+    Consist = apps.get_model("consist", "Consist")
+
+    for consist in Consist.objects.all():
+        try:
+            consist.scale = consist.consist_item.first().rolling_stock.scale
+            consist.save()
+        except AttributeError:
+            pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("consist", "0016_alter_consistitem_order"),
+        (
+            "metadata",
+            "0024_remove_genericdocument_tags_delete_decoderdocument_and_more",
+        ),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="consist",
+            name="scale",
+            field=models.ForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                to="metadata.scale",
+            ),
+        ),
+        migrations.RunPython(
+            set_scale,
+            reverse_code=migrations.RunPython.noop
+        ),
+    ]