[bhoomik-codes]

Summary

Adds support for creating, importing, managing, and applying custom user themes via JSON files (Idle Fantasy Material 3 compatible format).

Users can now import custom palette files, select their imported themes from a dedicated dialog or the existing color scheme carousel, and have their chosen seed colors dynamically applied throughout the application on Android 6.0+ (API 23+).

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Why this is needed

• Personalization: Users were previously restricted to built-in presets (Miku, Asuka, Totoro, etc.) or system Monet (Android 12+ only).
• Universal Dynamic Theming: Allows users on older Android versions (API 23–31) to enjoy content-based Material dynamic theming derived from their custom theme seed colors using Material Color Utilities without requiring OS Monet engine support.
• Interoperability: Supports importing JSON palette definitions from community tools.

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What was done

1. JSON Parsing & Validation (ImportedTheme.kt):
   • Implemented a parser validating schema, size limits (≤ 256 KB), color format (hex/argb), base mode (light / dark), and extraction of primary seed and contrast colors.
2. Settings & In-Memory Caching (AppSettings.kt):
   • Added importedThemes, selectedCustomThemeId, importCustomThemes(), and deleteCustomTheme().
   • Built with an in-memory @Volatile cache to avoid re-parsing JSON on every property access, preserving strict performance requirements (per CONTRIBUTING.md).
3. Application Theming (BaseActivity.kt):
   • Applied custom seed color dynamic theming using DynamicColors.applyToActivityIfAvailable with DynamicColorsOptions.Builder().setContentBasedSource(...).
   • Operates universally on Android 6.0–14+ without gating behind isDynamicColorAvailable().
4. Theme Preference & Management UI (ThemeChooserPreference.kt, AppearanceSettingsFragment.kt):
   • Added preferences to import theme files, switch between custom themes, and delete themes.
   • Handled file reading asynchronously on Dispatchers.IO using runCatchingCancellable to prevent UI thread blockage/ANRs during cloud storage imports.
   • Handled proper activity recreation (postRestart()) when switching between custom themes.
   • Preserved card preview shapes in ThemeChooserPreference by tinting shapes directly with the seed color rather than flattening the card background.

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Files Changed

File	Changes
app/src/main/kotlin/.../core/prefs/ImportedTheme.kt	[New] Theme model and JSON parser for custom palette files.
app/src/main/kotlin/.../core/prefs/AppSettings.kt	Persistent storage, in-memory cache, and management methods for imported custom themes.
app/src/main/kotlin/.../core/prefs/ColorScheme.kt	Added CUSTOM entry to the available color schemes list when custom themes exist.
app/src/main/kotlin/.../core/ui/BaseActivity.kt	Universal content-based theming via DynamicColorsOptions.setContentBasedSource(...).
app/src/main/kotlin/.../settings/AppearanceSettingsFragment.kt	UI for file picker import, selection dialog, deletion, and coroutine-based async reading.
app/src/main/kotlin/.../settings/utils/ThemeChooserPreference.kt	Preview rendering with shape tinting and refresh() method.
app/src/main/res/values/strings.xml	String resources for custom theme management dialogs and actions.
app/src/main/res/values/themes.xml	Added ThemeOverlay.Futon.Custom.Light and ThemeOverlay.Futon.Custom.Dark.
app/src/main/res/xml/pref_appearance.xml	Added preference entries for managing, importing, and deleting custom themes.

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Verification

• Tested compilation via ./gradlew compileDebugKotlin (Build succeeded).
• Zero new external dependencies added (complies with CONTRIBUTING.md APK size rule).
• File I/O executed on Dispatchers.IO (complies with performance rule).
• Preserved docstrings and existing coding standards.

[LandWarderer2772]

Tested on my phone running android 17, works as expected.

[bhoomik-codes]

So, you are going to merge it ?