feat(search): add wallpaper blur behind option for pixel search

[Balajitechlabs]

Description

Reworked this PR following review feedback to keep the native launcher feel intact.

Instead of overriding themes or handling back gestures manually in Compose (which broke the widget animations and predictive back), this keeps Theme.Essentials.WallpaperTranslucent and simply toggles native window blur (FLAG_BLUR_BEHIND) behind the wallpaper.

• Leaves the native launcher widget expand/collapse animations and system Predictive Back completely untouched.
• Adds a "Blur" toggle in Pixel Searchbar Settings (visible on Android 12+).
• Updates window blur in onResume / onNewIntent so toggling it applies right away.
• Adjusts the background scrim contrast automatically so search results stay easy to read whether blur is turned on, off, or disabled by battery saver.

Type of change

• Bug fix
• New feature
• UI / visual update
• Performance improvement
• Refactoring / cleanup
• Translations
• Build / CI tooling

UI changes

• Added a new Blur ("Blur the wallpaper background") toggle under Search Results in Pixel Searchbar Settings (Android 12+).

Checklist

Before submitting, please make sure:

• The base branch is set to develop (not main).
• The app builds cleanly locally with ./gradlew assembleDebug.
• Unit tests pass with ./gradlew testDebugUnitTest.
• You tested the changes on a device or emulator (including Shizuku or Root if applicable).
• New preferences use SettingsRepository for keys and getter/setter methods.
• New user-facing settings are registered in FeatureRegistry.kt for search indexing.
• New UI follows the design system in ui/core/ (RoundedCardContainer, IconToggleItem, etc.).
• Strings are added to res/values/strings.xml and drawables use rounded variants (R.drawable.rounded_*).

[sameerasw]

This change breaks predictive back gesture

[Balajitechlabs]

Thanks for catching this! Fixed in the latest commit 🥇 :}

[sameerasw]

No this is not the behavior we had before. This is just custom hand made animations animating while listening to back gesture. Not the initial animations we had in the launcher open and close animation or the search from the widget.

If we can not fix predictive back gesture and animation, this change is not worth it. Because it breaks the whole flow of the searchbar to act as an overlay rather than the search opening right from the widget and then closing back into it.

[Balajitechlabs]

Hey @sameerasw, updated! Removed the custom theme and back handler so the native widget animations and predictive back work properly. Tested on device and works great now.

[Balajitechlabs]

now shd work for you :)