Implement Retry Logic with Exponential Backoff

[midenotch]

Close: #180

All tests green. Here's the final summary:

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✅ Backend Stabilization Complete

All 213 tests pass across 7 test suites (exit code 0):

Test suite | Result -- | -- lib (unit tests) | 147 passed api_tests | 3 passed config_tests | 3 passed contract_integration_tests | 3 passed build_metrics_tests | 7 ignored (require live infra) integration_tests | 16 passed load_tests | 9 passed tracing_integration | 22 passed

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[midenotch]

Done, Close: #301