hotfix(backend): Fix month credit calculation on December (#8851)

When calculating the next month, we are not rolling the month number
causing an error on credits.

### Changes 🏗️

Add modulo while calculating next month.

### Checklist 📋

#### For code changes:
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#### For configuration changes:
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  <summary>Examples of configuration changes</summary>

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autogpt_platform/backend/backend/data/credit.py

@@ -70,7 +70,7 @@ class UserCredit(UserCreditBase):
     async def get_or_refill_credit(self, user_id: str) -> int:
         cur_time = self.time_now()
         cur_month = cur_time.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-        nxt_month = cur_month.replace(month=cur_month.month + 1)
+        nxt_month = cur_month.replace(month=cur_month.month % 12 + 1)
 
         user_credit = await UserBlockCredit.prisma().group_by(
             by=["userId"],