fix: Add no-cache header on HTML and favicon handler to prevent 404

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

main.go

@@ -54,6 +54,7 @@ func main() {
 		}
 		data, _ := fs.ReadFile(webFS, "web/index.html")
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.Header().Set("Cache-Control", "no-cache, must-revalidate")
 		w.Write(data)
 	})
 
@@ -71,6 +72,11 @@ func main() {
 	mux.HandleFunc("POST /f/{id}/auth", h.AuthSubmit)
 	mux.HandleFunc("DELETE /f/{id}", h.Delete)
 
+	// Favicon (prevent 404)
+	mux.HandleFunc("GET /favicon.ico", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusNoContent)
+	})
+
 	// Health
 	mux.HandleFunc("GET /health", func(w http.ResponseWriter, _ *http.Request) {
 		w.Header().Set("Content-Type", "application/json")