Log exceptions instead of silently swallowing them in calculate

[MaxGhenis]

Summary

• Replace silent pass in axes exception handler with logging.exception() so errors are visible in production logs
• Remove redundant print() in the non-axes path (now handled by the shared logging.exception())
• The axes code path previously discarded all exceptions silently, causing variables to return null with no trace (e.g., the NJ reform bug reported in clone()-based reform path breaks ParameterNode iteration, silently fails for NJ #3322)

Fixes #3322

Test plan

• Verify exception logging works by checking Cloud Logging after deployment
• Existing tests unaffected (no behavioral change for callers — just logging added)

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.24%. Comparing base (0ab47d3) to head (20dee2b).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
policyengine_api/country.py	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3323      +/-   ##
==========================================
+ Coverage   72.20%   72.24%   +0.04%     
==========================================
  Files          56       56              
  Lines        2425     2425              
  Branches      423      423              
==========================================
+ Hits         1751     1752       +1     
+ Misses        595      594       -1     
  Partials       79       79              

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