refactor: Improve exception handling and logging in authentication and playlist services; enhance code readability and structure

app/services/credit.py

@@ -223,11 +223,11 @@ class CreditService:
                     user_id,
                 )
 
-            return transaction
-
         except Exception:
             await session.rollback()
             raise
+        else:
+            return transaction
         finally:
             await session.close()
 
@@ -316,11 +316,11 @@ class CreditService:
                     user_id,
                 )
 
-            return transaction
-
         except Exception:
             await session.rollback()
             raise
+        else:
+            return transaction
         finally:
             await session.close()
 
@@ -503,11 +503,11 @@ class CreditService:
                     user_id,
                 )
 
-            return transaction
-
         except Exception:
             await session.rollback()
             raise
+        else:
+            return transaction
         finally:
             await session.close()