Fix hardcoded SQLite '?' placeholders across all payment modules for MySQL compatibility

- Add DatabaseManager.placeholder property returning '?' (SQLite) or '%s' (MySQL)
- Fix paypal_handler.py: payment_methods INSERT
- Fix service.py: payment_methods INSERT for PayPal vault
- Fix subscription/manager.py: all SQL in create/upgrade/downgrade/cancel_subscription
- Fix subscription/renewal.py: all SQL in process_renewals/_renew_subscription/_cancel_subscription
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

aisbf/database.py

@@ -166,6 +166,10 @@ class DatabaseManager:
         else:
             raise ValueError(f"Unsupported database type: {self.db_type}")
     
+    @property
+    def placeholder(self) -> str:
+        return '?' if self.db_type == 'sqlite' else '%s'
+
     async def _run_in_executor(self, func, *args):
         """Run a blocking database operation in a thread pool executor."""
         loop = asyncio.get_event_loop()

aisbf/payments/fiat/paypal_handler.py

@@ -280,10 +280,11 @@ class PayPalPaymentHandler:
                 # Store payment method
                 with self.db._get_connection() as conn:
                     cursor = conn.cursor()
-                    cursor.execute("""
+                    ph = self.db.placeholder
+                    cursor.execute(f"""
                         INSERT INTO payment_methods
                         (user_id, type, identifier, is_default, is_active)
-                        VALUES (?, 'paypal', ?, 1, 1)
+                        VALUES ({ph}, 'paypal', {ph}, 1, 1)
                     """, (user_id, agreement_id))
                     conn.commit()
                 

aisbf/payments/service.py

@@ -182,10 +182,11 @@ class PaymentService:
             # Store payment method
             with self.db._get_connection() as conn:
                 cursor = conn.cursor()
-                cursor.execute("""
+                ph = self.db.placeholder
+                cursor.execute(f"""
                     INSERT INTO payment_methods
                     (user_id, type, gateway, identifier, paypal_email, is_default, status)
-                    VALUES (?, 'paypal', 'paypal_v3', ?, ?, 1, 'active')
+                    VALUES ({ph}, 'paypal', 'paypal_v3', {ph}, {ph}, 1, 'active')
                 """, (user_id, result['payment_token_id'], result['payer_email']))
                 conn.commit()