Upgrade AGP and replace kotlin-android-extensions with viewbinding

[Rajan-p-simform]

This pull request introduces several changes to modernize the codebase, improve compatibility, and enhance maintainability. Key updates include upgrading SDK versions, transitioning from synthetic view binding to Android View Binding.

Build Configuration Updates:

• SSffmpegVideoOperation/build.gradle: Upgraded compileSdk to 35, targetSdkVersion to 35. Added a flatDir repository for local libraries. [1] [2]
• app/build.gradle: Updated compileSdk and targetSdkVersion to 35, replaced kotlin-android-extensions with viewBinding.

View Binding Migration:

• BaseActivity.kt: Removed setContentView logic from the base class to allow individual activities to set views using View Binding.
• Migrated synthetic view binding to View Binding in multiple activity files (MainActivity.kt, OtherFFMPEGProcessActivity.kt, VideoProcessActivity.kt, AudiosMergeActivity.kt).