fix(deps): security updates (#201)

## Dependabot Rust security remediation (personal-sysadmin/Cargo.lock)

### Fixed
- **rand**: `0.9.2` -> `0.9.3` (low severity advisory; patched in-range
via `cargo update`).

### Flagged — not auto-fixable
- **hickory-proto (medium, patched 0.26.1)**: blocked. Current `0.25.2`
is locked by `libp2p-mdns 0.48.0` -> `libp2p 0.56.0`, whose requirement
is `^0.25.2`. The patched `0.26.1` is a MAJOR bump outside the range, so
`cargo update` cannot reach it without a manifest major upgrade of
`libp2p`. **needs-manual-major** (0.25.2 -> 0.26.1).
- **hickory-proto (high, patched NONE)**: **no-patch-available** — no
fixed version exists upstream for this advisory. Updating to 0.26.1
(even if libp2p were bumped) is not guaranteed to address it.

No Cargo.toml or checksum hand-edits were made. Do not merge until
reviewed.

Author: hyperpolymath