fix: don't redirect to /u/{handle}/ on private (multi-user) instances

site/src/lib/manifest.ts

@@ -22,6 +22,17 @@ export interface ShardHandle {
   url: string;
 }
 
+export function isInstancePrivate(): boolean {
+  try {
+    const dataDir = findDataDir();
+    if (!dataDir) return false;
+    const root = JSON.parse(readFileSync(join(dataDir, 'index.json'), 'utf-8'));
+    return root?.instance?.private === true;
+  } catch {
+    return false;
+  }
+}
+
 export function readShardHandles(): ShardHandle[] {
   try {
     const dataDir = findDataDir();