Develop - Code refactor and optimization, Battery widget improvements

[sameerasw]

This pull request makes several important updates to the build configuration and refines Kotlin/Java code style and imports across the project. The most significant changes include upgrading the Android and Java/Kotlin toolchains, updating dependencies, and cleaning up code formatting and imports for better readability and maintainability.

Build system and dependency upgrades:

• Upgraded the Kotlin jvmTarget to JVM_21 and Java source/target compatibility to VERSION_21, ensuring the project uses the latest language features. Also updated compileSdk and targetSdk to version 37 for improved Android platform support. [1] [2]
• Added new experimental Compose APIs to the Kotlin compiler optIn list, enabling the use of cutting-edge Compose features.
• Updated the androidx.compose.material3:material3 dependency from 1.5.0-alpha17 to 1.5.0-alpha19.

Code cleanup and formatting:

• Improved import statements in multiple files by removing unused imports, adding missing ones, and reordering for clarity, particularly in AppLockActivity.kt, AppUpdatesActivity.kt, and FeatureSettingsActivity.kt. [1] [2] [3] [4] [5] [6] [7] [8]
• Reformatted and simplified code in several places for better readability, such as splitting long lines, improving variable assignments, and removing redundant code in EssentialsApp.kt and FeatureSettingsActivity.kt. [1] [2] [3] [4] [5]

Compose UI simplification:

• Replaced fully qualified Compose UI component references with direct imports for Text and other components in AppUpdatesActivity.kt, resulting in cleaner and more idiomatic Compose code. [1] [2] [3] [4] [5]
• Reformatted Compose UI code blocks for improved consistency and readability, such as splitting parameters across multiple lines.

These changes collectively modernize the codebase, improve maintainability, and ensure compatibility with the latest Android and Compose features.