feat: Implement robust error/not-found pages & UI components

- Introduce dedicated error pages for dashboard and video routes
- Add specific not-found pages for dashboard, projects, videos, and settings
- Implement global `not-found.tsx` for general unhandled routes
- Integrate root and dashboard layouts with ErrorBoundary and Suspense
- Add new UI components: Accordion, Hover Card, Menubar, Navigation Menu, Select, Tabs
- Update Navbar to utilize the new Navigation Menu component
- Enhance `button` component with a `link` variant for better styling
- Refine existing UI components (dialog, dropdown, input, etc.)
- Update Tailwind config with new colors and animation extensions

app/watch/[videoId]/not-found.tsx

@@ -0,0 +1,25 @@
+import Link from "next/link";
+import { Button } from "@/components/ui/button";
+import { Film, XCircle } from "lucide-react";
+
+export default function WatchNotFound() {
+  return (
+    <div className="flex min-h-screen flex-col items-center justify-center gap-4 p-4">
+      <div className="flex flex-col items-center gap-2 text-center">
+        <div className="relative">
+          <Film className="h-12 w-12 text-muted-foreground" />
+          <XCircle className="absolute -bottom-1 -right-1 h-6 w-6 text-destructive" />
+        </div>
+        <h1 className="text-2xl font-bold">Video Not Found</h1>
+        <p className="text-muted-foreground max-w-md">
+          The video you&apos;re looking for doesn&apos;t exist, has been removed, or the link may be expired.
+        </p>
+      </div>
+      <div className="flex gap-2">
+        <Button asChild variant="default">
+          <Link href="/">Go home</Link>
+        </Button>
+      </div>
+    </div>
+  );
+}