feat: implement AutoStartHelper and improve background permission flows

[DinanathDash]

Overview

This PR extracts and improves the background execution stability by introducing an AutoStartHelper and refining the permission dialog flows.

This pull request was split from the original PR #123 to make reviewing easier as requested.

Changes Included

• AutoStartHelper: Added a new utility to guide users on enabling auto-start permissions, which is critical for background service reliability on heavily modified Android ROMs (like MIUI, ColorOS).
• Service Integration: Updated AirSyncService to integrate with the new auto-start checks.
• Permissions Flow: Enhanced PermissionsActivity, PermissionsScreen, and PermissionDialog to provide clearer rationale when asking for background and auto-start permissions.
• Manifest: Added necessary declarations in AndroidManifest.xml to support the background operations.

[sameerasw]

Putting this on draft as location permission was not approved by Google Play and was found not justifiable. Will try again later maybe