Implement tasks 25, 26 + completion visibility setting

Task 25: Multiple dashboards — dashboards table + migration, /d/[slug]
route, root redirect, dashboard tabs in nav with create/rename/delete/
set-default. Task 26: Editable dashboard — react-grid-layout drag/resize
editor, widget picker modal with per-widget configurator auto-generated
from default config, save/reset server actions with Zod validation.

Completion visibility: server-side per-user setting (hours) replaces
localStorage timer; queries filter completed items by updatedAt cutoff;
Settings page dropdown persists preference via server action.

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

src/components/dashboard-tab.tsx

@@ -0,0 +1,22 @@
+"use client";
+
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+
+export function DashboardTab({ slug, name }: { slug: string; name: string }) {
+  const pathname = usePathname();
+  const isActive = pathname === `/d/${slug}` || pathname.startsWith(`/d/${slug}/`);
+
+  return (
+    <Link
+      href={`/d/${slug}`}
+      className={`shrink-0 px-3 py-2 text-sm transition-colors border-b-2 ${
+        isActive
+          ? "border-primary text-foreground"
+          : "border-transparent text-muted-foreground hover:text-foreground"
+      }`}
+    >
+      {name}
+    </Link>
+  );
+}