refactor(crypto): split curve primitives

[robwoodgate]

Stacked: #661 @ 31371a6

Summary

• split curve-specific crypto primitives into curve_bls.ts and curve_secp.ts
• move shared curve dispatch helpers into curves.ts
• keep NUT modules focused on protocol coordination by importing narrower curve helpers
• document the v5 deep-import migration note for crypto/core users

Validation

• npm run check-lint
• npm run compile
• npx vitest run --project node --project browser test/crypto/core.test.ts test/crypto/NUT12.test.ts test/crypto/NUT13.test.ts test/crypto/NUT01.test.ts test/crypto/bls.test.ts test/model/OutputData.bls.test.ts
• npm run check-format
• pre-push lint/format hook passed

[codecov]

Codecov Report

❌ Patch coverage is 96.15385% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.34%. Comparing base (a80dbf4) to head (a34d4fb).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/crypto/curve_secp.ts	97.22%	1 Missing ⚠️
src/crypto/curves.ts	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #667      +/-   ##
==========================================
+ Coverage   92.32%   92.34%   +0.02%     
==========================================
  Files          51       53       +2     
  Lines        4952     4952              
  Branches     1217     1217              
==========================================
+ Hits         4572     4573       +1     
  Misses        160      160              
+ Partials      220      219       -1     

Flag	Coverage Δ
integration	38.59% <57.69%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.