Remove accept filter on full-backup restore file input

iPadOS greys out .tar.gz files when the input has an accept filter, so
the archive could not be selected. The server validates the gzip
signature and archive contents before restoring, so no client-side
filter is needed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/AnalyticsPanel.tsx

@@ -827,10 +827,11 @@ export function AnalyticsPanel({
       </div>
       <div className="admin-restore-row">
         <label htmlFor="full-backup-file">Restore from File</label>
+        {/* No accept filter: iPadOS greys out .tar.gz with one — the server
+            validates the archive contents before restoring anyway. */}
         <input
           id="full-backup-file"
           type="file"
-          accept=".tar.gz,.tgz,application/gzip,application/x-gzip"
           onChange={e => setFullBackupFile(e.target.files?.[0] ?? null)}
           disabled={fullBackupBusy}
         />