Fix axum route params: use :param syntax (not {param}) for axum 0.7

Axum 0.7 uses :param for path parameters. {param} is axum 0.8+ syntax.
Routes were silently not matching, causing 404 on all key lookups.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/crates/warzone-server/src/routes/messages.rs

@@ -11,8 +11,8 @@ use crate::state::AppState;
 pub fn routes() -> Router<AppState> {
     Router::new()
         .route("/messages/send", post(send_message))
-        .route("/messages/poll/{fingerprint}", get(poll_messages))
-        .route("/messages/{id}/ack", delete(ack_message))
+        .route("/messages/poll/:fingerprint", get(poll_messages))
+        .route("/messages/:id/ack", delete(ack_message))
 }
 
 #[derive(Deserialize)]