Support Safe Notes on iOS devices

[keshav-space]

Minimium feature needed to support Safe Notes on iOS:

• Initial support for iOS platform #183
• Add biometric support on iOS #189
• Add backup support for iOS devices #191
• Add text button to open the backup folder in native file explorer #193
• UI: Simplify Dark Mode Settings #198
• Show app version in settings #200
• Refactor Android secure display to use native API #203
• Add support for secure display on iOS #205
• Add Splash screen for iOS
• Redirect Rate App to Apple store on ios devices
• Optimize image with ImgBot
• Figure out an appropriate license for the App Store; GPL may be problematic
• Translation updates
  • Update backup description and translation for: Instead of daily backup, Safe Notes now intelligently performs continuous backup.
  • Add translation for: "Use device's light or dark mode setting for the app." Ref Simplify dark mode settings #199
  • Add translation for: "Theme" Ref Simplify dark mode settings #199
• Update the F-Droid recipe to use proper JDK and Flutter version.
• Publish beta test version to https://testflight.apple.com/
• Publish to iOS App store.