feat: use simpler m2m relationship for specialization

src/fellchensammlung/migrations/0057_delete_speciesspecialization.py

@@ -0,0 +1,16 @@
+# Generated by Django 5.2.1 on 2025-07-14 05:15
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('fellchensammlung', '0056_alter_rescueorganization_options_and_more'),
+    ]
+
+    operations = [
+        migrations.DeleteModel(
+            name='SpeciesSpecialization',
+        ),
+    ]