fix(deps): bump rustls-webpki 0.103.12 -> 0.103.13 (GHSA-82j2-j2ch-gfr8)

Resolves the rustls-webpki CRL BIT STRING DoS (GHSA-82j2-j2ch-gfr8 /
RUSTSEC-2026-0104, CVSS 7.5 HIGH, fixed in 0.103.13). Transitive dep
via rustls; lockfile-only bump (cargo update -p rustls-webpki).

Closes Dependabot alert #4. Addresses issue #16 (the two findings in
#16, GHSA-82j2-j2ch-gfr8 and RUSTSEC-2026-0104, are the same advisory).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hyperpolymath