feat(theme): add roundedraff theme and fix sleep cover crop grid artifacts (#918)

## Summary
- Add new `roundedraff` theme.
- Fix sleep screen artifact where book cover showed grid lines in
`Cover` mode with `Crop`.

## Additional Context
## Key changes
- Added `src/components/themes/roundedraff/` theme implementation.
- Updated sleep cover rendering logic in:
  - `src/activities/boot_sleep/SleepActivity.cpp`
  - `src/activities/boot_sleep/SleepActivity.h`
- Improved cover generation/regeneration paths in:
  - `lib/Epub/Epub.cpp`
  - `lib/Epub/Epub.h`
  - `lib/Txt/Txt.cpp`
  - `lib/Txt/Txt.h`

## Verification
- Sleep screen set to Book cover
- Sleep screen cover mode set to Crop
- Confirmed grid artifacts no longer appear on cover sleep screen.

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**< YES >**_

---------

Co-authored-by: CaptainFrito <yzq6x5zypy@privaterelay.appleid.com>
Co-authored-by: Zach Nelson <zach@zdnelson.com>
Co-authored-by: Uri Tauber <142022451+Uri-Tauber@users.noreply.github.com>

lib/I18n/translations/czech.yaml

@@ -202,6 +202,7 @@ STR_FILTER_CONTRAST: "Kontrast"
 STR_UI_THEME: "Šablona rozhraní"
 STR_THEME_CLASSIC: "Klasická"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Oprava blednutí na slunci"
 STR_REMAP_FRONT_BUTTONS: "Přemapovat přední tlačítka"

lib/I18n/translations/english.yaml

@@ -228,6 +228,7 @@ STR_BATTERY: "Battery"
 STR_UI_THEME: "UI Theme"
 STR_THEME_CLASSIC: "Classic"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Sunlight Fading Fix"
 STR_REMAP_FRONT_BUTTONS: "Remap Front Buttons"

lib/I18n/translations/french.yaml

@@ -225,6 +225,7 @@ STR_BATTERY: "Batterie"
 STR_UI_THEME: "Thème interface"
 STR_THEME_CLASSIC: "Classique"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Correction lisibilité au soleil"
 STR_REMAP_FRONT_BUTTONS: "Configurer boutons façade"

lib/I18n/translations/german.yaml

@@ -225,6 +225,7 @@ STR_BATTERY: "Batterie"
 STR_UI_THEME: "System-Design"
 STR_THEME_CLASSIC: "Klassisch"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Anti-Verblassen"
 STR_REMAP_FRONT_BUTTONS: "Vordere Tasten belegen"

lib/I18n/translations/portuguese.yaml

@@ -202,6 +202,7 @@ STR_FILTER_CONTRAST: "Contraste"
 STR_UI_THEME: "Tema da interface"
 STR_THEME_CLASSIC: "Clássico"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Ajuste desbotamento ao sol"
 STR_REMAP_FRONT_BUTTONS: "Remapear botões frontais"

lib/I18n/translations/russian.yaml

@@ -225,6 +225,7 @@ STR_BATTERY: "Батарея"
 STR_UI_THEME: "Тема интерфейса"
 STR_THEME_CLASSIC: "Классическая"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra Extended"
 STR_SUNLIGHT_FADING_FIX: "Компенсация выцветания"
 STR_REMAP_FRONT_BUTTONS: "Переназначить передние кнопки"

lib/I18n/translations/spanish.yaml

@@ -226,6 +226,7 @@ STR_UI_THEME: "Interfaz"
 STR_THEME_CLASSIC: "Clásico"
 STR_THEME_LYRA: "Lyra"
 STR_THEME_LYRA_EXTENDED: "Lyra Extendido"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_SUNLIGHT_FADING_FIX: "Corrección de desvanecimiento"
 STR_REMAP_FRONT_BUTTONS: "Reconfigurar botones frontales"
 STR_OPDS_BROWSER: "Navegador OPDS"

lib/I18n/translations/swedish.yaml

@@ -228,6 +228,7 @@ STR_BATTERY: "Batteri"
 STR_UI_THEME: "Användargränssnittstema"
 STR_THEME_CLASSIC: "Klassisk"
 STR_THEME_LYRA: "Lyra"
+STR_THEME_ROUNDEDRAFF: "RoundedRaff"
 STR_THEME_LYRA_EXTENDED: "Lyra utökad"
 STR_SUNLIGHT_FADING_FIX: "Fix för solskensmattning"
 STR_REMAP_FRONT_BUTTONS: "Ändra frontknappar"