chore(init): scaffold OpenFrame — Next.js + Bun + shadcn

Initialize OpenFrame project with core scaffold and UI foundation.

- Project scaffold: Next.js 16.1 (App Router) + Bun runtime
- UI: shadcn/ui + TailwindCSS; landing, dashboard, project, and auth UIs
- Video support: provider abstraction (YouTube first), video player page with timestamped comments and custom timeline
- Auth & DB: NextAuth skeleton and Prisma schema (Postgres) included
- UX: dark-mode toggle, full-width layouts, comments sidebar, video route moved to /watch/[videoId]
- Dev: added YouTube iframe integration, custom controls, and TypeScript types
- Next steps: DB migrations, API routes (CRUD), real data wiring, voice-recording & sharing

components/theme-toggle.tsx

@@ -0,0 +1,42 @@
+'use client';
+
+import * as React from 'react';
+import { Moon, Sun } from 'lucide-react';
+import { useTheme } from 'next-themes';
+import { Button } from '@/components/ui/button';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+
+export function ThemeToggle() {
+  const { setTheme, theme } = useTheme();
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="ghost" size="icon">
+          <Sun className="h-4 w-4 rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
+          <Moon className="absolute h-4 w-4 rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100" />
+          <span className="sr-only">Toggle theme</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        <DropdownMenuItem onClick={() => setTheme('light')}>
+          <Sun className="h-4 w-4 mr-2" />
+          Light
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme('dark')}>
+          <Moon className="h-4 w-4 mr-2" />
+          Dark
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme('system')}>
+          <span className="h-4 w-4 mr-2">💻</span>
+          System
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}