feat: add MTR display board and train info components

- Implemented MtrDisplayBoard component to show train schedules with weather information.
- Created MtrTrainInfo component to manage state and render MtrDisplayBoard.
- Added ScreenshotTaker component for downloading screenshots of the display board.
- Introduced theme toggle functionality with ThemeToggle component.
- Developed various UI components including Button, Card, ColorPicker, DropdownMenu, Input, Label, Popover, Select, Separator, Switch, Tabs, and Textarea.
- Added utility functions for class name merging and tool definitions.

src/components/nav.tsx

@@ -0,0 +1,20 @@
+import Link from "next/link";
+import { ThemeToggle } from "./theme-toggle";
+
+export function Navbar() {
+  return (
+    <header className="sticky top-0 z-50 w-full border-b bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
+      <div className="container flex h-14 px-4 items-center">
+        <div className="flex-1" />
+        <div className="flex-1 text-center">
+          <Link href="/" className="font-bold">
+            Web Tools
+          </Link>
+        </div>
+        <div className="flex flex-1 justify-end">
+          <ThemeToggle />
+        </div>
+      </div>
+    </header>
+  );
+}