Refactor: Shares-Funktionen in Datasets-Seite zusammengeführt

- datasets/page.tsx: neuer Tab 'Shares & Config' mit vollem Inhalt aus
  shares/page.tsx (Samba, NFS, Samba Config mit MacOS-Toggle + Raw-Editor)
- shares/page.tsx: redirect -> /datasets
- Header.tsx: 'Shares'-Link zeigt auf /datasets

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/components/Header.tsx

@@ -85,9 +85,9 @@ export function Header() {
               Navigator
             </Link>
             <Link
-              href="/shares"
+              href="/datasets"
               className={`px-3 py-2 rounded-md text-sm font-medium transition-colors ${
-                isActive("/shares")
+                isActive("/datasets")
                   ? "bg-accent text-accent-foreground"
                   : "text-muted-foreground hover:text-foreground"
               }`}
@@ -205,9 +205,9 @@ export function Header() {
               Files
             </Link>
             <Link
-              href="/shares"
+              href="/datasets"
               className={`block px-3 py-2 rounded-md text-sm font-medium ${
-                isActive("/shares")
+                isActive("/datasets")
                   ? "bg-accent text-accent-foreground"
                   : "text-muted-foreground hover:text-foreground"
               }`}