chore(deps): drop unmaintained rustls-pemfile; axum-server 0.7 -> 0.8

axum-server was used only for the plain-HTTP nvhttp listener, but we enabled
its tls-rustls feature (HTTPS is hand-rolled over tokio-rustls) — and that
feature was what pulled the unmaintained rustls-pemfile (RUSTSEC-2025-0134).
Drop the feature, bump axum-server to 0.8 (0.8 also no longer pulls it), and
move our own PEM parsing in gamestream/tls.rs to rustls-pki-types' PemObject
(the same path punktfunk-core/quic.rs already uses), removing our direct
rustls-pemfile dep too.

Net: rustls-pemfile fully gone; dependency graph trimmed 547 -> 529 crates
(the tls-rustls feature also dragged in prettyplease + a wasm-tooling chain).
cargo audit now reports only audiopus_sys + paste (transitive, latest, no
successor). 108 host tests + clippy + fmt green.

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

.cargo/audit.toml

@@ -5,8 +5,11 @@
 # means the audit job stops flagging it, so the reasoning must hold up.
 #
 # NOTE: `cargo audit` (no `--deny warnings`) fails only on *vulnerabilities*, not on the
-# `unmaintained` warnings (audiopus_sys / paste / rustls-pemfile). Those are left visible on purpose
-# so we keep getting the maintenance signal — they do not fail CI.
+# `unmaintained` warnings (audiopus_sys via opus, paste via utoipa-axum). Both are transitive, at
+# their latest published version with no successor, so there's nothing to bump — left visible on
+# purpose so we keep getting the maintenance signal; they do not fail CI. (rustls-pemfile was dropped
+# 2026-06-29 by removing axum-server's unused tls-rustls feature + moving our own PEM parsing to
+# rustls-pki-types; memmap2's unsoundness was fixed by the 0.9.11 bump.)
 
 [advisories]
 ignore = [