feat(web): exibe erros ao enfileirar e melhora acessibilidade e contraste

- Mostra no formulário o erro devolvido pela API ao enfileirar (antes só ia ao console) e desabilita o botão durante o envio.
- Adiciona aria-label no campo de URL, role=alert no erro e role=progressbar na barra.
- Clareia a cor destructive (contraste do texto de erro sobre o fundo escuro ~2:1 para ~4,5:1).
- Corrige o título da página (era 'web').

web/index.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <link rel="icon" type="image/svg+xml" href="/vite.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>web</title>
+    <title>Ephemeral Downloader</title>
   </head>
   <body>
     <div id="root"></div>

web/src/App.tsx

@@ -35,14 +35,6 @@ function DownloadList() {
 function Main() {
   const { queueDownload } = useSession();
 
-  const handleDownload = async (url: string) => {
-    try {
-      await queueDownload(url);
-    } catch (error) {
-      console.error("Failed to queue", error);
-    }
-  };
-
   return (
     <Layout>
       <div className="grid gap-8 lg:grid-cols-12">
@@ -56,7 +48,7 @@ function Main() {
                   Paste a link to start. Files are downloaded to the server first.
                 </p>
               </div>
-              <DownloadForm onDownload={handleDownload} />
+              <DownloadForm onDownload={queueDownload} />
             </section>
 
             <Alert variant="destructive">

web/src/components/feature/DownloadForm.tsx

@@ -9,14 +9,15 @@ const formSchema = z.object({
 });
 
 interface DownloadFormProps {
-    onDownload: (url: string) => void;
+    onDownload: (url: string) => Promise<void>;
 }
 
 export function DownloadForm({ onDownload }: DownloadFormProps) {
     const [url, setUrl] = useState("");
     const [error, setError] = useState<string | null>(null);
+    const [submitting, setSubmitting] = useState(false);
 
-    const handleSubmit = (e: React.FormEvent) => {
+    const handleSubmit = async (e: React.FormEvent) => {
         e.preventDefault();
         setError(null);
 
@@ -27,8 +28,15 @@ export function DownloadForm({ onDownload }: DownloadFormProps) {
             return;
         }
 
-        onDownload(url);
-        setUrl("");
+        setSubmitting(true);
+        try {
+            await onDownload(url);
+            setUrl("");
+        } catch (err) {
+            setError(err instanceof Error ? err.message : "Failed to queue download");
+        } finally {
+            setSubmitting(false);
+        }
     };
 
     return (
@@ -37,14 +45,21 @@ export function DownloadForm({ onDownload }: DownloadFormProps) {
                 <div className="flex-1 space-y-1">
                     <Input
                         type="url"
+                        aria-label="File URL"
+                        aria-invalid={error ? true : undefined}
+                        aria-describedby={error ? "url-error" : undefined}
                         placeholder="https://example.com/file.zip"
                         value={url}
                         onChange={(e) => setUrl(e.target.value)}
                         className={error ? "border-destructive focus-visible:ring-destructive" : ""}
                     />
-                    {error && <p className="text-xs text-destructive">{error}</p>}
+                    {error && (
+                        <p id="url-error" role="alert" className="text-xs text-destructive">
+                            {error}
+                        </p>
+                    )}
                 </div>
-                <Button type="submit">
+                <Button type="submit" disabled={submitting}>
                     <Download className="mr-2 h-4 w-4" />
                     Download
                 </Button>

web/src/components/ui/ProgressBar.tsx

@@ -14,6 +14,10 @@ const Progress = React.forwardRef<HTMLDivElement, ProgressProps>(
         return (
             <div
                 ref={ref}
+                role="progressbar"
+                aria-valuemin={0}
+                aria-valuemax={max}
+                aria-valuenow={percent}
                 className={cn(
                     "relative h-2 w-full overflow-hidden rounded-full bg-secondary",
                     className

web/src/context/SessionContext.tsx

@@ -90,7 +90,7 @@ export function SessionProvider({ children }: { children: React.ReactNode }) {
     }, [sessionId]);
 
     const queueDownload = async (url: string) => {
-        if (!sessionId) return;
+        if (!sessionId) throw new Error("Session not ready, try again in a moment");
         try {
             const res = await fetch(`${API_URL}/api/queue`, {
                 method: "POST",
@@ -101,7 +101,10 @@ export function SessionProvider({ children }: { children: React.ReactNode }) {
                 body: JSON.stringify({ url }),
             });
 
-            if (!res.ok) throw new Error("Failed to queue download");
+            if (!res.ok) {
+                const body = (await res.json().catch(() => null)) as { error?: string } | null;
+                throw new Error(body?.error || "Failed to queue download");
+            }
 
             await refreshTasks(); // Immediate refresh
 

web/src/index.css

@@ -45,7 +45,7 @@
     --accent: 217.2 32.6% 17.5%;
     --accent-foreground: 210 40% 98%;
 
-    --destructive: 0 62.8% 30.6%;
+    --destructive: 0 72% 54%;
     --destructive-foreground: 210 40% 98%;
 
     --border: 217.2 32.6% 17.5%;