feat: Add placeholder chat handler

Add empty Messages function in chat.go as foundation for future
real-time chat functionality. Currently a no-op but provides the
basic handler structure needed for WebSocket chat integration.

router/handlers/chat.go

@@ -0,0 +1,7 @@
+package handlers
+
+import "net/http"
+
+func Messages(w http.ResponseWriter, r *http.Request) {
+
+}