Fixed iOS Build Issues with Static Frameworks

[subhankarmaiti]

Description

This PR addresses critical issues that were preventing successful builds for users on iOS:

1. Enhanced Swift header imports in A0Auth0.mm to work correctly with static frameworks. The implementation now uses preprocessor directives to check for the header file in different locations:
   • First tries importing from the module path <A0Auth0/A0Auth0-Swift.h>
   • Falls back to the local import "A0Auth0-Swift.h" if the module import is not available

Issues Resolved

• Fixes 'A0Auth0-Swift.h' file not found #1180
• Fixes Using static linking in Podfile causes undefined symbol error when building #986

Testing Done

• Verified that pod installation works successfully with the updated bundler version
• Confirmed that builds complete successfully in projects using static frameworks