Update dependencies and fix audit findings
Backend:
- cargo update: rustls 0.23.40 -> 0.23.45 (RUSTSEC-2026-0285), plus
semver-compatible bumps (actix-web 4.15, tokio 1.53, diesel 2.3.13, ...)
- Disable actix-web's `http2` feature: the server binds plain HTTP/1.1,
and the feature pulls in the unmaintained h2 0.3 line (RUSTSEC-2026-0258)
Frontend:
- Update all packages within their ranges, fixing 8 npm audit findings
(nanoid, postcss, undici, ...)
- vitest 4 -> 5
- Remove unused unreadCount in RssFeeds.vue (lint error)
mathias
81f5f0f722