Fix error handling in auth0 ul customize to gracefully ignore specific prompt errors

[developerkunal]

🔧 Changes

This PR improves error handling for the auth0 ul customize functionality, ensuring that specific prompt-related errors (such as "Your account does not have custom prompts" or "feature is not available for your plan") are gracefully ignored. This change prevents the function from failing due to these non-critical issues and enhances the robustness of the system.

• Improved error checking for specific API responses related to unavailable features.
• Updated relevant test cases to ensure proper handling of ignored errors.

📚 References

N/A

🔬 Testing

This change was tested with updated unit tests that verify:

• Error handling for unavailable prompts or features, ensuring these errors are safely ignored.
• Manual End-to-end testing with various branding settings and prompt customizations to validate system behaviour in different scenarios.

📝 Checklist

• All new/changed functionality is covered by tests
• I have added documentation for all new/changed functionality (or N/A)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.05%. Comparing base (5ce0e13) to head (ec9e6a5).

Files with missing lines	Patch %	Lines
internal/cli/universal_login_customize.go	77.77%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1081   +/-   ##
=======================================
  Coverage   72.05%   72.05%           
=======================================
  Files          94       94           
  Lines       12938    12942    +4     
=======================================
+ Hits         9322     9326    +4     
  Misses       3069     3069           
  Partials      547      547           

Flag	Coverage Δ
	72.05% <77.77%> (+<0.01%)	⬆️

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