chore(simulator): add health endpoint and permissive cors

[trevortrinh]

What

• adds /health endpoint
• adds permissive cors

Why

Required for local testing with the explorer. Without these, the explorer fails to load blocks and gets stuck on the loading.

Before	After

[patrick-ogrady]

🙏

[codecov-commenter]

Codecov Report

❌ Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.95%. Comparing base (1b98ffe) to head (3517e39).
⚠️ Report is 1 commits behind head on local-simulator.

Files with missing lines	Patch %	Lines
simulator/src/lib.rs	40.00%	3 Missing ⚠️

@@                 Coverage Diff                 @@
##           local-simulator     #144      +/-   ##
===================================================
- Coverage            56.98%   56.95%   -0.03%     
===================================================
  Files                   20       20              
  Lines                 2908     2913       +5     
===================================================
+ Hits                  1657     1659       +2     
- Misses                1251     1254       +3     

Files with missing lines	Coverage Δ
simulator/src/lib.rs	93.51% <40.00%> (-0.68%)	⬇️

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