feat(finance): add payment method field and post-festival accounting tools

- Add Payment.method field (cash/card/paypal/bank) with migration
- Show method in PaymentAdmin list view
- Add merge_users management command (atomic, reassigns all FKs)
- Add update_crates_2026 command (actual purchased/returned crates)
- Add finance_summary_2026 command (Ausgaben, Einnahmen, Kasse, Bilanz)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gaehsnitz/admin.py

@@ -210,8 +210,8 @@ class DonationAdmin(admin.ModelAdmin):
 
 @admin.register(Payment)
 class PaymentAdmin(admin.ModelAdmin):
-    list_display = ("date", "purpose", "amount")
-    list_filter = ("date",)
+    list_display = ("date", "purpose", "amount", "method")
+    list_filter = ("method", "date")
     ordering = ("-date",)
     search_fields = ("purpose",)
 

gaehsnitz/management/commands/finance_summary_2026.py

@@ -0,0 +1,86 @@
+from decimal import Decimal, ROUND_HALF_UP
+
+from django.core.management.base import BaseCommand
+from django.db.models import F, Sum
+
+from gaehsnitz.models import Consumption, Payment, UserPayment
+
+
+YEAR = 2026
+CASH_PREFILL = Decimal("500.00")
+
+
+def eur(amount):
+    return str(Decimal(amount).quantize(Decimal("1"), rounding=ROUND_HALF_UP))
+
+
+class Command(BaseCommand):
+    help = "Print full 2026 festival finance summary"
+
+    def handle(self, *args, **options):
+        w = self.stdout.write
+        sep = "-" * 40
+
+        # --- Ausgaben ---
+        w("\nAUSGABEN")
+        w(sep)
+        payments = Payment.objects.filter(date__year=YEAR).order_by("date")
+        total_out = Decimal("0")
+        for p in payments:
+            method_label = dict(Payment.Method.choices).get(p.method, p.method)
+            w(f"  {p.date}  {eur(p.amount):>6}€  {method_label:<15}  {p.purpose}")
+            total_out += p.amount
+        w(sep)
+        w(f"  {'TOTAL':<11} {eur(total_out):>6}€")
+
+        # by method
+        w("")
+        for method, label in Payment.Method.choices:
+            subtotal = payments.filter(method=method).aggregate(s=Sum("amount"))["s"] or Decimal("0")
+            if subtotal:
+                w(f"    {label:<15} {eur(subtotal):>6}€")
+
+        # --- Einnahmen ---
+        w("\nEINNAHMEN")
+        w(sep)
+        up = UserPayment.objects.filter(created_at__year=YEAR)
+
+        cash_prefill = CASH_PREFILL
+        cash_payments = up.filter(method="cash").aggregate(s=Sum("amount"))["s"] or Decimal("0")
+        cash_from_sales = cash_payments - cash_prefill
+
+        non_cash = up.exclude(method="cash").aggregate(s=Sum("amount"))["s"] or Decimal("0")
+
+        total_in = cash_from_sales + non_cash
+
+        drink_revenue = Consumption.objects.filter(for_free=False, drink__year=YEAR).annotate(
+            cost=F("amount") * F("drink__sale_price_per_bottle")
+        ).aggregate(s=Sum("cost"))["s"] or Decimal("0")
+        entry_donations = total_in - drink_revenue
+
+        w(f"  Cash:                {eur(cash_from_sales):>6}€")
+        w(f"  Cashless:            {eur(non_cash):>6}€")
+        w(f"  Einnahmen Gesamt:    {eur(total_in):>6}€")
+        w(f"  - Getränke-Umsatz:   {eur(drink_revenue):>6}€")
+        w(f"  - Eintrittsspenden:  {eur(entry_donations):>6}€")
+
+        # --- Kassensaldo ---
+        w("\nKASSE")
+        w(sep)
+        cash_out = payments.filter(method="cash").aggregate(s=Sum("amount"))["s"] or Decimal("0")
+        expected_cash = cash_prefill + cash_from_sales - cash_out
+        w(f"  Kassen-Vorschuss:  {eur(cash_prefill):>6}€")
+        w(f"  Cash-Einnahmen:    {eur(cash_from_sales):>6}€")
+        w(f"  Cash-Ausgaben:     {eur(cash_out):>6}€")
+        w(f"  -> in Kasse:       {eur(expected_cash):>6}€")
+
+        # --- Gesamtbilanz ---
+        w("\nGESAMTBILANZ")
+        w(sep)
+        net = total_in - total_out
+        out_of_pocket = total_out - total_in
+        w(f"  Gesamtausgaben:   {eur(total_out):>6}€")
+        w(f"  Gesamteinnahmen:  {eur(total_in):>6}€")
+        w(sep)
+        label = "Verlust" if out_of_pocket > 0 else "Gewinn"
+        w(f"  {label}:          {eur(abs(net)):>6}€\n")

gaehsnitz/management/commands/merge_users.py

@@ -0,0 +1,46 @@
+from django.core.management.base import BaseCommand, CommandError
+from django.db import transaction
+
+from gaehsnitz.models import User
+
+
+class Command(BaseCommand):
+    help = "Merge source user into target user, then delete source"
+
+    def add_arguments(self, parser):
+        parser.add_argument("source", help="Username of user to merge FROM (will be deleted)")
+        parser.add_argument("target", help="Username of user to merge INTO (will be kept)")
+
+    def handle(self, *args, **options):
+        source_name = options["source"]
+        target_name = options["target"]
+
+        if source_name == target_name:
+            raise CommandError("Source and target must be different users")
+
+        try:
+            source = User.objects.get(username=source_name)
+        except User.DoesNotExist:
+            raise CommandError(f"Source user '{source_name}' not found")
+
+        try:
+            target = User.objects.get(username=target_name)
+        except User.DoesNotExist:
+            raise CommandError(f"Target user '{target_name}' not found")
+
+        with transaction.atomic():
+            payments = source.user_payments.count()
+            consumptions = source.consumption_list.count()
+
+            source.user_payments.update(user=target)
+            source.consumption_list.update(user=target)
+
+            source.delete()
+
+        self.stdout.write(
+            self.style.SUCCESS(
+                f"Merged '{source_name}' into '{target_name}': "
+                f"{payments} payment(s), {consumptions} consumption(s) reassigned. "
+                f"Source user deleted."
+            )
+        )

gaehsnitz/management/commands/update_crates_2026.py

@@ -0,0 +1,39 @@
+from django.core.management.base import BaseCommand
+from django.db import transaction
+
+from gaehsnitz.models import Drink
+
+# Actual crates bought from supplier (all others were returned full, no cost)
+# (name, crates_ordered, crates_purchased)
+# crates_returned = crates_purchased (all empties back, full deposit refunded)
+ACTUAL_CRATES = [
+    ("Sternburg Export", 12, 11),
+    ("Ur-Krostitzer", 5, 2),
+    ("Budweiser", 5, 2),
+    ("Altenburger Helles", 5, 5),
+    ("Feldschl. Radler", 2, 1),
+    ("Lübzer Grapef. 0,0", 1, 1),
+    ("Freiberger 0,0", 4, 3),
+    ("Club Mate", 2, 2),
+    ("Vita Cola", 2, 1),
+    ("Paulaner Spezi", 2, 2),
+    ("Wasser", 10, 5),
+]
+
+
+class Command(BaseCommand):
+    help = "Update 2026 drink crates to actual purchased amounts"
+
+    def handle(self, *args, **options):
+        with transaction.atomic():
+            for name, ordered, purchased in ACTUAL_CRATES:
+                updated = Drink.objects.filter(name=name, year=2026).update(
+                    crates_ordered=ordered,
+                    crates_purchased=purchased,
+                    crates_returned=purchased,
+                )
+                if updated:
+                    self.stdout.write(f"  {name}: ordered={ordered}, purchased={purchased}, returned={purchased}")
+                else:
+                    self.stdout.write(self.style.WARNING(f"  NOT FOUND: {name}"))
+        self.stdout.write(self.style.SUCCESS("Done."))

gaehsnitz/migrations/0011_add_payment_method.py

@@ -0,0 +1,18 @@
+# Generated by Django 6.0.6 on 2026-06-20 12:06
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('gaehsnitz', '0010_add_sekt_category'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='payment',
+            name='method',
+            field=models.CharField(choices=[('cash', 'Bar'), ('card', 'EC-Karte'), ('paypal', 'PayPal'), ('bank', 'Überweisung')], default='paypal', max_length=16, verbose_name='Methode'),
+        ),
+    ]

gaehsnitz/models.py

@@ -73,9 +73,16 @@ class Payment(models.Model):
         bands = 11, "Bands"
         supply_purchase = 12, "Getränke-/Essenseinkauf"
 
+    class Method(models.TextChoices):
+        cash = "cash", "Bar"
+        card = "card", "EC-Karte"
+        paypal = "paypal", "PayPal"
+        bank = "bank", "Überweisung"
+
     purpose = models.CharField("Zweck", max_length=64)
     date = models.DateField("Datum")
     amount = PriceField("Betrag")
+    method = models.CharField("Methode", max_length=16, choices=Method.choices, default=Method.paypal)
 
     class Meta:
         verbose_name = "Ausgabe"