Short description of changes

There are four very small changes to tidy up src/main.ccp in this pull request:

• Minor formatting changes
  This commit literally adjusts spacing for consistency.
• Adjust #ifdef block
  To avoid strange handling of a { ... } block, I've adjusted a #ifdef position and duplicated a line of code.
• Adjust "use translations"
  At the point bUseTranslation is used, we will only use the result in the GUI, so code adjusted to avoid duplication.
• Use single application exec
  We always declare and assign pApp to something with an exec() method and we only create one instance that can be executed, so duplicate code removed for clarity.

CHANGELOG: Refactor src/main.cpp

Context: Fixes an issue?

Refactoring for good code hygiene.

Does this change need documentation? What needs to be documented and how?

No change to application behaviour.

Status of this Pull Request

Can be merged.

What is missing until this pull request can be merged?

Can be merged after review.

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above