Refactor email confirmation handling to delegate to the client

[girgisadel]

Refactor email confirmation logic to delegate to the client side

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Summary of the changes (Less than 80 chars)

Description

This PR introduces a new ClientOptions class to encapsulate client-specific configuration for email confirmation URLs, and updates the IdentityOptions and IdentityApiEndpointRouteBuilderExtensions classes to support these configurations.

changes allow greater flexibility in customizing the email confirmation URL, moving the responsibility to the client-side rather than the back-end.

Fixes #59647

[girgisadel]

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