chore(deps): bump rustls to 0.23.45 for RUSTSEC-2026-0285

[shane-moore]

Problem, Evidence, and Context (Required)

• cargo audit fails on every PR against unstable and epbs since RUSTSEC-2026-0285 (2026-09-14): rustls 0.23.41 accepts TLS 1.3 handshake messages across encryption level boundaries, medium severity (5.3).
• Blocks check-code on all open PRs, e.g. feat(message_validator): admit batched builder request auth partial signatures #1302.
• Same shape as the h2 bump in chore(deps): bump h2 to 0.4.16 for RUSTSEC-2026-0258 #1266.

Change Overview (Required)

• Lockfile only: rustls 0.23.41 -> 0.23.45, rustls-webpki 0.103.13 -> 0.103.15 (required transitive bump).
• rustls is not a direct dependency, so no manifest change.

Risks, Trade-offs, and Mitigations (Required)

• Patch-level bump of a TLS library used through reqwest and the beacon node client paths. Blast radius is any outbound HTTPS.
• Mitigated by staying within the 0.23 minor line and by the compile and audit checks below.

Validation (Required)

• make audit-CI: 0 vulnerabilities, 10 allowed warnings (unchanged).
• cargo check --locked --workspace: clean.

Rollback (Required for behavior or runtime changes; optional otherwise)

• Revert the lockfile change. No config or data impact.

Blockers / Dependencies (Optional)

• After merge, epbs needs a merge from unstable so PRs against it pick up the fix.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.13%. Comparing base (ad86525) to head (90f244c).
⚠️ Report is 1 commits behind head on unstable.

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable    #1303   +/-   ##
=========================================
  Coverage     71.13%   71.13%           
=========================================
  Files           168      168           
  Lines         30536    30536           
=========================================
  Hits          21721    21721           
  Misses         8815     8815           

Flag	Coverage Δ
rust	71.13% <ø> (ø)

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