Web dav file access impl

[sameerasw]

This pull request introduces a new feature that allows users to mount their Android device storage as a local drive on macOS using WebDAV. It adds the necessary UI, settings, and logic to enable or disable this feature, and ensures it is only available to AirSync+ users. The changes also include localization updates and integration with the existing device connection workflow.

New File Access Feature (WebDAV integration):

• Added a new WebDAVManager class to handle mounting and unmounting the Android device storage as a WebDAV volume in macOS Finder, including methods for mounting, unmounting, and opening the volume in Finder. (airsync-mac/Core/Storage/WebDAVManager.swift)
• Integrated WebDAV mounting/unmounting into the app lifecycle: mounts the volume when a compatible device connects and unmounts it when disconnected or on app launch; also cleans up stale mounts. (airsync-mac/Core/AppState.swift) [1] [2]

Settings and User Interface:

• Added a new toggle in the Settings view to enable or disable File Access, with a description and gating for AirSync+ users (including a popover explaining the feature restriction). (airsync-mac/Screens/Settings/SettingsView.swift)
• Added a "Browse Files" button to the menubar for quick access to the mounted Android volume. (airsync-mac/Screens/MenubarView/MenubarSegments.swift)

Localization and User Experience:

• Updated localization strings to include new menu and settings items for File Access. (airsync-mac/Localization/en.json) [1] [2]

Access Control and State Management:

• Enforced that File Access is only available to AirSync+ users by disabling the toggle and auto-reverting the setting if the user is not eligible. Also ensures UserDefaults and state are kept in sync and unmounts the drive if access is revoked. (airsync-mac/Core/AppState.swift) [1] [2] [3]