fix: retry transient Monarch transaction updates

[eshaffer321]

Summary

• retry idempotent Monarch transaction updates once after retryable 5xx or network timeout errors
• return immediately for permanent failures and caller cancellation
• preserve per-attempt intent/completion records in the API audit trail
• cover every retry-classification branch with regression tests
• build CI and release artifacts with Go 1.25.13, which fixes the standard-library vulnerabilities reported against 1.25.12

Verification

• go test ./...
• go test ./... -race
• go run golang.org/x/vuln/cmd/govulncheck@v1.3.0 ./... — no vulnerabilities found
• pre-commit formatting, golangci-lint, and go vet ./...
• targeted Amazon dry-run completed with zero errors (the previously affected order was already repaired and skipped)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.95%. Comparing base (3d1ed22) to head (e647441).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #86      +/-   ##
==========================================
+ Coverage   64.70%   64.95%   +0.25%     
==========================================
  Files          50       51       +1     
  Lines        6969     6979      +10     
==========================================
+ Hits         4509     4533      +24     
+ Misses       2118     2108      -10     
+ Partials      342      338       -4     

Flag	Coverage Δ
unittests	64.95% <100.00%> (+0.25%)	⬆️

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Files with missing lines	Coverage Δ
internal/application/sync/consolidator.go	85.88% <ø> (+1.77%)	⬆️
internal/application/sync/monarch_retry.go	100.00% <100.00%> (ø)
internal/application/sync/types.go	39.77% <100.00%> (+9.36%)	⬆️

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