Refactor API and add transaction list tool

[dcramer]

• Add 'list_transactions' endpoint
• Move API into its own submodule (getting a little large)
• Improve some tool responses and expand coverage

We cant yet reliable export a trace until Sentry lands some new APIs, so considering this a PoC.

[codecov]

Codecov Report

Attention: Patch coverage is 91.71484% with 43 lines in your changes missing coverage. Please review.

Project coverage is 82.18%. Comparing base (4ccd825) to head (2cfc6c7).
Report is 3 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lib/sentry-api/client.ts	75.00%	18 Missing ⚠️
src/lib/sentry-msw.ts	93.46%	13 Missing ⚠️
src/mcp/tools.ts	90.72%	9 Missing ⚠️
src/lib/sentry-api/utils.ts	91.89%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
+ Coverage   79.09%   82.18%   +3.08%     
==========================================
  Files          15       18       +3     
  Lines        1765     2110     +345     
  Branches       97      135      +38     
==========================================
+ Hits         1396     1734     +338     
- Misses        369      376       +7     

Flag	Coverage Δ
evals	25.54% <30.63%> (?)
unittests	80.57% <91.68%> (+1.47%)	⬆️

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