Return planned workout editors to their originating page

[Felixre7]

I know you said this was a feature not a bug but the current behavior is a little unintuitive. I think people expect the back arrow to go back to the last viewed page. fixes: #870

Validation:

• Tested an Android release build on the emulator: saved workout edits, toolbar Back, Android Back, nested exercise editing, and the Settings-to-plan path.
• Tested on pixel 9 pro hardware
• Changed-file lint, formatting, and React Compiler lint pass.

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