ci: enforce clippy -D warnings and cargo audit as hard gates

Flip both CI gates from informational to hard-fail (SPEC-001 quality gates):
- clippy: `-- -D warnings` on the server crate. Cleared the debt via clippy --fix
  (unused imports/style), targeted #[allow(dead_code)] on native-remote-control
  future API, and #[allow(clippy::too_many_arguments)] on 3 protocol-mirroring fns.
- cargo audit: hard-fail with documented per-ID --ignore flags (rsa RUSTSEC-2023-0071
  unfixable/unreachable in active tree; gtk-rs + glib Linux-only tray backend not
  compiled into the Windows agent; proc-macro-error build-time). New advisories fail.
- Move [profile.release] to the workspace root (it was silently ignored in the server
  member), activating lto/codegen-units/strip.

No behavioral changes. Reviewed and gates verified passing on the build host.

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

server/src/api/mod.rs

@@ -8,7 +8,7 @@ pub mod releases;
 pub mod users;
 
 use axum::{
-    extract::{Path, Query, State},
+    extract::{Path, State},
     Json,
 };
 use serde::{Deserialize, Serialize};
@@ -78,12 +78,14 @@ impl From<crate::session::Session> for SessionInfo {
 }
 
 /// List all active sessions
+#[allow(dead_code)] // TODO(native-remote-control): consumed by the integration API; see docs/specs/native-remote-control/
 pub async fn list_sessions(State(sessions): State<SessionManager>) -> Json<Vec<SessionInfo>> {
     let sessions = sessions.list_sessions().await;
     Json(sessions.into_iter().map(SessionInfo::from).collect())
 }
 
 /// Get a specific session by ID
+#[allow(dead_code)] // TODO(native-remote-control): consumed by the integration API; see docs/specs/native-remote-control/
 pub async fn get_session(
     State(sessions): State<SessionManager>,
     Path(id): Path<String>,