fix(transactions): keep a recurrence on its day after a short month

A monthly recurrence on the 31st clamped to Feb 28 and stayed on the
28th for every later month.

app/apps/transactions/models.py

@@ -1,3 +1,4 @@
+import calendar
 import decimal
 import logging
 import uuid
@@ -1183,7 +1184,21 @@ class RecurringTransaction(TransferTemplate):
             return relativedelta(years=self.recurrence_interval)
 
     def get_next_date(self, current_date):
-        return current_date + self.get_recurrence_delta()
+        next_date = current_date + self.get_recurrence_delta()
+
+        # A start on the 29th-31st is clamped in shorter months; return to that day
+        # afterwards instead of keeping the clamped one.
+        if (
+            self.recurrence_type
+            in (self.RecurrenceType.MONTH, self.RecurrenceType.YEAR)
+            and self.start_date.day > current_date.day
+            and current_date.day
+            == calendar.monthrange(current_date.year, current_date.month)[1]
+        ):
+            last_day = calendar.monthrange(next_date.year, next_date.month)[1]
+            next_date = next_date.replace(day=min(self.start_date.day, last_day))
+
+        return next_date
 
     @classmethod
     def generate_upcoming_transactions(cls):

app/apps/transactions/tests/test_models.py

@@ -242,6 +242,30 @@ class RecurringTransactionTests(TestCase):
         self.assertEqual(recurring.recurrence_interval, 1)
         self.assertEqual(recurring.account.currency.code, "USD")
 
+    def test_month_end_recurrence_returns_to_its_day(self):
+        """A recurrence on the 31st goes back to it after a short month"""
+        recurring = RecurringTransaction.objects.create(
+            account=self.account,
+            type=Transaction.Type.EXPENSE,
+            amount=Decimal("100.00"),
+            description="Rent",
+            start_date=datetime.date(2026, 1, 31),
+            recurrence_type=RecurringTransaction.RecurrenceType.MONTH,
+            recurrence_interval=1,
+        )
+
+        feb = recurring.get_next_date(datetime.date(2026, 1, 31))
+        march = recurring.get_next_date(feb)
+        april = recurring.get_next_date(march)
+
+        self.assertEqual(feb, datetime.date(2026, 2, 28))
+        self.assertEqual(march, datetime.date(2026, 3, 31))
+        self.assertEqual(april, datetime.date(2026, 4, 30))
+        self.assertEqual(
+            recurring.get_next_date(datetime.date(2026, 2, 1)),
+            datetime.date(2026, 3, 1),
+        )
+
     def test_generate_upcoming_transactions_keeps_tags_and_entities(self):
         """Generation must copy tags/entities even with no current user"""
         tag = TransactionTag.objects.create(name="Essential")