test: detect R.string duplicates of backend translations

A number of my recent code reviews were flagging that strings added to R.string
already exist in `TR` (`GeneratedTranslations`).

To fix this, iterate the English strings from both TR and R.string, and fail
 if there are duplicates not defined in one of two BASELINE_ variables and
 produce copy-pasteable BASELINE text when the backend is updated

This test:
* Automates my review comments
* Produces copy-pasteable BASELINE text when the backend is updated
  * Allowing a fast fix of the test
* Lists opportunities where we can remove duplicated strings
  * Reducing APK size
  * Including `.toSentenceCase()` fixes
* Ensures the baseline list is updated when strings are fixed

The format of BASELINE entries lists all the `R.string` and `TR` cases:
 In some cases, there can be a many:many mapping, and a developer needs
 to decide which to select:

```
* R.string.deck_conf_general | R.string.pref_cat_general
* TR.preferencesGeneral() | TR.schedulingGeneral()
```

Assisted-by: Claude Opus 4.6

Code was written by Claude, with much re-prompting
 for comment formatting, abstractions and code changes
 Code/comments were manually refactored and made less verbose

Author: david-allison