Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

models/production_output.py

@@ -14,7 +14,8 @@ class ProductionOutput(Base):
     unit_symbol = Column(String(16), nullable=True)
 
     scenario = relationship(
-        "Scenario", back_populates="production_output_items")
+        "Scenario", back_populates="production_output_items"
+    )
 
     def __repr__(self):
         return (