fix(rustproxy-routing): reduce hot-path allocations in routing, metrics, and proxy protocol handling

rust/crates/rustproxy-routing/src/route_manager.rs

@@ -60,6 +60,16 @@ impl RouteManager {
         manager
     }
 
+    /// Check if any route on the given port uses header matching.
+    /// Used to skip expensive header HashMap construction when no route needs it.
+    pub fn any_route_has_headers(&self, port: u16) -> bool {
+        if let Some(indices) = self.port_index.get(&port) {
+            indices.iter().any(|&idx| self.routes[idx].route_match.headers.is_some())
+        } else {
+            false
+        }
+    }
+
     /// Find the best matching route for the given context.
     pub fn find_route<'a>(&'a self, ctx: &MatchContext<'_>) -> Option<RouteMatchResult<'a>> {
         // Get routes for this port