Split worker trace job persistence helpers

[yvette-carlisle]

Summary

• Split worker trace job SQL persistence insert helpers into worker/trace_jobs/persistence.rs.
• Kept parent trace_jobs.rs focused on payload decoding, transaction orchestration, and commit order.
• Preserved helper signatures, SQL, conflict handling, and narrow pub(super) visibility.

Validation

• cargo make fmt-rust
• cargo make check-rust
• cargo make fmt-rust-check
• git diff --check
• cargo make lint-vstyle
• cargo nextest run -p elf-worker --all-targets --all-features (6 passed)
• cargo make lint-rust
• cargo make test-rust (379 passed, 92 skipped)
• cargo make check (379 passed, 92 skipped)
• Docker-backed cargo make test-rust-integration (92 passed, 379 skipped)
• Docker-backed cargo make check-trace-gate

Review

• Scout selected trace persistence as a strong modularization boundary.
• Skeptic passed with no findings after staged diff review.