fix(deps): update dependencies and fix security vulnerabilities (#37)

Bumps version to 0.8.3 and updates all dependencies via `just update`
(nix flake + cargo update) to resolve 5 security advisories flagged by
`cargo audit`:

- **RUSTSEC-2026-0007**: `bytes` integer overflow in `BytesMut::reserve`
(→ 1.11.1)
- **RUSTSEC-2026-0049**: `rustls-webpki` faulty CRL matching logic (→
0.103.10)
- **RUSTSEC-2026-0067**: `tar` `unpack_in` symlink chmod escalation (→
0.4.45)
- **RUSTSEC-2026-0068**: `tar` incorrect PAX size header handling (→
0.4.45)
- **RUSTSEC-2026-0009**: `time` DoS via stack exhaustion (→ 0.3.47)

Author: tembleking