Implement alias selection and summary fetching in incident and live pages

- Added functionality to manage and display available aliases for incidents and live updates, enhancing user interaction.
- Refactored alias handling to use checkboxes for selection, improving usability and clarity in the UI.
- Integrated fetching of aggregated summary data to populate available aliases dynamically, ensuring up-to-date information.
- Updated the logic for applying selected aliases in API requests, streamlining data retrieval based on user preferences.

internal/server/gateway.go

@@ -356,6 +356,13 @@ func (s *statusWriter) WriteHeader(code int) {
 	s.ResponseWriter.WriteHeader(code)
 }
 
+// Flush keeps streaming compatibility (SSE/EventSource) through middleware wrappers.
+func (s *statusWriter) Flush() {
+	if f, ok := s.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
 // Shutdown idle connections on the shared transport.
 func (g *Gateway) Shutdown(ctx context.Context) error {
 	g.transport.CloseIdleConnections()