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[sameerasw]

This pull request introduces a new "Self Compiled" build configuration for AirSync, making it easier for users to build and use the app with all Plus features unlocked for personal use. The changes include updates to the Xcode project, new documentation for local building, adjustments to licensing logic for self-compiled builds, and improvements to localization and acknowledgments.

Build and Configuration Improvements:

• Added a new "Self Compiled" build configuration and scheme to the Xcode project (AirSync.xcodeproj), including relevant settings and a dedicated xcconfig file that defines the SELF_COMPILED compilation condition. This allows users to build a version of AirSync with Plus features enabled without a license key. [1] [2] [3] [4] [5]
• Updated the README.md with clear instructions for building and archiving the "Self Compiled" version locally.

Licensing and Feature Unlocking:

• Modified app logic to automatically unlock Plus features and set the license state when the SELF_COMPILED flag is present, bypassing online license checks and enabling all premium functionality for self-compiled builds. [1] [2] [3] [4] [5] [6] [7] [8]

Documentation and Acknowledgments:

• Added LottieUI to the acknowledgments section in the README.md.

Localization:

• Improved and expanded the German translation file (de.json) for better clarity and accuracy.

Miscellaneous:

• Updated the custom sponsorship URL in .github/FUNDING.yml to point to the new store.
• Minor update to the Xcode scheme version for compatibility.
• Added an autocreated test plan reference to the main scheme.

These changes make it significantly easier for contributors and users to build AirSync locally with all features enabled, while also improving the project's documentation, internationalization, and build system robustness.