Add ML-KEM support (PKCS#11 v3.2 / FIPS 203)

[MatthiasValvekens]

• Declare constants for ML-KEM mechanisms & parameter sets
• Python wrappers for C_EncapsulateKey and C_DecapsulateKey (PKCS#11 v3.2 API)
• Handle ML-KEM key attributes & keygen logic

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 91.08911% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.48%. Comparing base (fc44b72) to head (0500389).

Files with missing lines	Patch %	Lines
pkcs11/_pkcs11.pyx	89.61%	8 Missing ⚠️
pkcs11/mechanisms.py	88.88%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #241      +/-   ##
==========================================
- Coverage   91.52%   91.48%   -0.04%     
==========================================
  Files          15       15              
  Lines        2713     2808      +95     
  Branches       27       27              
==========================================
+ Hits         2483     2569      +86     
- Misses        228      237       +9     
  Partials        2        2              

Flag	Coverage Δ
unittests	91.48% <91.08%> (-0.04%)	⬇️

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