Update app labels for billing, writer, and planner models; fix foreign key references in automation migrations

- Set app labels for CreditTransaction and CreditUsageLog models to 'billing'.
- Updated app labels for Tasks, Content, and Images models to 'writer'.
- Changed foreign key references in automation migrations from 'account' to 'tenant' for consistency.

backend/igny8_core/business/billing/models.py

@@ -24,6 +24,7 @@ class CreditTransaction(AccountBaseModel):
     created_at = models.DateTimeField(auto_now_add=True)
     
     class Meta:
+        app_label = 'billing'
         db_table = 'igny8_credit_transactions'
         ordering = ['-created_at']
         indexes = [
@@ -61,6 +62,7 @@ class CreditUsageLog(AccountBaseModel):
     created_at = models.DateTimeField(auto_now_add=True)
     
     class Meta:
+        app_label = 'billing'
         db_table = 'igny8_credit_usage_logs'
         ordering = ['-created_at']
         indexes = [