fix: ensure fetcher honors token_type

[frederikprijck]

This PR ensures that the Fetcher honors the token_type when DPoP is configured:

• If the token_type is bearer, we will not set the DPoP scheme and the DPoP header.
• if the token_type is dpop, we will set both.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.44%. Comparing base (483663a) to head (d82a554).

Files with missing lines	Patch %	Lines
src/server/fetcher.ts	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2365      +/-   ##
==========================================
+ Coverage   85.18%   86.44%   +1.25%     
==========================================
  Files          37       37              
  Lines        4051     4064      +13     
  Branches      777      793      +16     
==========================================
+ Hits         3451     3513      +62     
+ Misses        597      548      -49     
  Partials        3        3              

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