fix: split inverted orientation label from color filter label (#2421)

## Summary

* **What is the goal of this PR?** 
* Fix the “Inverted” translation so reader orientation and color/filter
inversion can use separate labels.
* **What changes are included?**
* Adds `STR_ORIENTATION_INVERTED` for the inverted portrait orientation
option.
* Updates the reader orientation setting to use
`STR_ORIENTATION_INVERTED` instead of reusing `STR_INVERTED`.
* Leaves `STR_INVERTED` for the sleep cover filter and tilt page-turn
mode
  * Adds the new orientation string across all 26 locale YAML files.

## Additional Context

* The original issue was found by a user in German, where `STR_INVERTED`
was translated as `Hochformat 180°`, which made sense for orientation
but not for color filters.
* This is a UI-label-only change. It does not change persisted
orientation values or settings behavior.
* Reviewer note: non-English wording may still benefit from
native-speaker review, especially for the new orientation-specific
labels and to verify the interchangeable usage between inverted color
and inverted tilt page turn direction.
---

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lib/I18n/translations/slovenian.yaml

@@ -132,7 +132,8 @@ STR_SLEEP: "Spanje"
 STR_PAGE_TURN: "Obračanje strani"
 STR_PORTRAIT: "Pokončno"
 STR_LANDSCAPE_CW: "Ležeče (v smeri urinega kazalca)"
-STR_INVERTED: "Obrnjeno"
+STR_INVERTED: "Invertirano"
+STR_ORIENTATION_INVERTED: "Pokončno 180°"
 STR_LANDSCAPE_CCW: "Ležeče (proti smeri urinega kazalca)"
 STR_PREV_NEXT: "Nazaj/Naprej"
 STR_NEXT_PREV: "Naprej/Nazaj"