feat: add presigned jwt support

[Tolsto]

This pull request adds support for pre-signed JWTs as an alternative authentication method, fixing a limitation where private keys must be supplied directly. The current approach doesn't work with security hardware like Smartcards or Cloud HSMs where private keys can't be accessed directly.

Definition of Ready

• I am happy with the code
• Short description of the feature/issue is added in the pr description
• PR is linked to the corresponding user story
• Acceptance criteria are met
• All open todos and follow ups are defined in a new ticket and justified
• Deviations from the acceptance criteria and design are agreed with the PO and documented.
• No debug or dead code
• My code has no repetitions
• Critical parts are tested automatically
• Where possible E2E tests are implemented
• Documentation/examples are up-to-date
• All non-functional requirements are met
• Functionality of the acceptance criteria is checked manually on the dev system.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 31 lines in your changes missing coverage. Please review.

Project coverage is 0.05%. Comparing base (ecb8f77) to head (cb18eb4).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/client/zitadel/client.go	0.00%	16 Missing ⚠️
pkg/client/middleware/auth.go	0.00%	8 Missing ⚠️
pkg/client/auth.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #432      +/-   ##
==========================================
- Coverage    0.05%    0.05%   -0.01%     
==========================================
  Files         130      130              
  Lines      107727   107757      +30     
==========================================
  Hits           57       57              
- Misses     107667   107697      +30     
  Partials        3        3              

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[livio-a]

Hey @Tolsto thanks for the contribution!

If you want a small gift as a thank you, please reach out to [email protected]

[github-actions]

🎉 This PR is included in version 3.4.0 🎉

The release is available on GitHub release

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