Fix: preserve non-ASCII filenames in document downloads (#9702)

src-ui/src/app/utils/http.ts

@@ -0,0 +1,23 @@
+export function getFilenameFromContentDisposition(header: string): string {
+  if (!header) {
+    return null
+  }
+
+  // Try filename* (RFC 5987)
+  const filenameStar = header.match(/filename\*=(?:UTF-\d['']*)?([^;]+)/i)
+  if (filenameStar?.[1]) {
+    try {
+      return decodeURIComponent(filenameStar[1])
+    } catch (e) {
+      // Ignore decoding errors and fall through
+    }
+  }
+
+  // Fallback to filename=
+  const filenameMatch = header.match(/filename="?([^"]+)"?/)
+  if (filenameMatch?.[1]) {
+    return filenameMatch[1]
+  }
+
+  return null
+}