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

app/schemas/auth.py

@@ -84,7 +84,9 @@ class ApiTokenStatusResponse(BaseModel):
 class ChangePasswordRequest(BaseModel):
     """Schema for password change request."""
 
-    current_password: str | None = Field(None, description="Current password (required if user has existing password)")
+    current_password: str | None = Field(
+        None, description="Current password (required if user has existing password)",
+    )
     new_password: str = Field(
         ...,
         min_length=8,