feat(host): Apollo-backlog hardening — cert gate, NVENC RFI, media QoS, async injector

A pass over the apollo-comparison backlog (re-verified against current code).
Lands four items end-to-end plus a Windows-DualSense scoping doc.

- #5/#92/#26 — GameStream paired-cert allow-list. tls.rs surfaces the verified
  peer cert to handlers (serve_https + PeerCertFingerprint, now shared with the
  mgmt API instead of duplicated); nvhttp gates /launch /resume /applist /cancel
  on AppState.paired and reports a real PairStatus; save_paired writes atomically
  (temp+rename). Closes the "mTLS accepts any client cert" hole. + regression test.

- #6/#51/#19/#22 — NVENC caps query -> reference-frame invalidation. nvenc.rs
  query_caps probes nvEncGetEncodeCaps (max dims / 10-bit / custom-VBV / RFI),
  rejecting over-range modes and degrading 10-bit->8-bit instead of an opaque
  InvalidParam. New Encoder::invalidate_ref_frames (default false -> caller
  keyframes); the Windows NVENC path implements real RFI (multi-ref DPB +
  nvEncInvalidateRefFrames, dedup + IDR-on-overflow). control.rs decodes the
  0x0301 lost-frame range (Apollo's IDX_INVALIDATE_REF_FRAMES) -> AppState.rfi_range
  -> encode loop, falling back to a keyframe. NOTE: the Windows NVENC impl is
  RTX-box/CI-pending (can't compile on Linux); adversarially reviewed vs the SDK.

- #43/#72 — media socket QoS + buffer growth. New punktfunk_core::transport::qos:
  grow_socket_buffers (factored out the native plane's 32MB SO_SNDBUF growth so the
  GameStream sockets reuse it) + set_media_qos (opt-in PUNKTFUNK_DSCP=1: DSCP CS5
  video / CS6 audio + Linux SO_PRIORITY, Apollo's scheme). Wired into UdpTransport
  and the GameStream video/audio sockets. Windows IP_TOS needs qWAVE (follow-up).

- #8/#45 — GameStream input injection off the ENet service thread. on_receive no
  longer injects inline (a slow inject head-blocked ENet keepalive/retransmit); it
  forwards to a dedicated injector thread. The hardened InjectorService moved from
  punktfunk1 into crate::inject (shared by both planes) + a coalesce step that sums
  adjacent relative-mouse/scroll deltas while preserving button/key/abs ordering.

Docs: re-verified apollo-comparison.md status (22 items already done/obsolete since
the snapshot) + windows-dualsense-scoping.md (ViGEm can't emulate a DualSense; real
DS5 on Windows needs a VHF virtual-HID driver — web-research pass pending).

fmt + clippy -D warnings clean; full workspace test suite green; no C-ABI/OpenAPI drift.

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

crates/punktfunk-host/src/gamestream/audio.rs

@@ -303,6 +303,9 @@ fn run(
     audio_cap: &std::sync::Mutex<Option<Box<dyn AudioCapturer>>>,
 ) -> Result<()> {
     let sock = UdpSocket::bind(("0.0.0.0", AUDIO_PORT)).context("bind audio UDP")?;
+    // Grow SO_SNDBUF/RCVBUF + opt-in DSCP/QoS-tag this as the audio class (PUNKTFUNK_DSCP=1).
+    punktfunk_core::transport::grow_socket_buffers(&sock);
+    punktfunk_core::transport::set_media_qos(&sock, punktfunk_core::transport::MediaClass::Audio);
     // The client pings the audio port (~every 500ms) so we learn where to send.
     sock.set_read_timeout(Some(Duration::from_secs(10)))?;
     tracing::info!(port = AUDIO_PORT, "audio: awaiting client ping");