fix: unwrap async params in download route segment

### Issue:
Next.js App Router expects params to be a Promise that must be awaited before accessing properties.

### Error:
```
Route "/download/[...segments]" used `params.segments`.
`params` is a Promise and must be unwrapped with `await`
or `React.use()` before accessing its properties.
```

### Solution:
- Made component async: `export default async function DownloadListing`
- Updated params type: `Promise<{ segments: string[] }>`
- Unwrapped with await: `const { segments: rawSegments } = await params`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

dashboard/src/app/download/[...segments]/page.tsx

@@ -68,12 +68,12 @@ function getLatestModified(listing: DirListing): string | undefined {
   return latest
 }
 
-export default function DownloadListing({
+export default async function DownloadListing({
   params,
 }: {
-  params: { segments: string[] }
+  params: Promise<{ segments: string[] }>
 }) {
-  const rawSegments = params.segments ?? []
+  const { segments: rawSegments } = await params
   const segments = rawSegments
     .map((segment) => segment.trim().replace(/\/+$/g, ''))
     .filter((segment) => segment.length > 0)