feat: add comprehensive GitHub workflow and development tools

app/stiftung/migrations/0018_destinataer_vierteljaehrlicher_betrag.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.0.6 on 2025-08-29 13:27
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stiftung', '0017_destinataer_haushaltsgroesse_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='destinataer',
+            name='vierteljaehrlicher_betrag',
+            field=models.DecimalField(blank=True, decimal_places=2, max_digits=12, null=True, verbose_name='Vierteljährlicher Betrag (€)'),
+        ),
+    ]