feat: integrate Tailwind CSS with custom theme and animations

Added Tailwind CSS and tw-animate-css imports to globals.css. Introduced a custom dark variant and an extensive @theme inline block with CSS variables for colors, radii, and animations. Included keyframes for shimmer-slide, spin-around, gradient, shine, and background-position-spin to enable consistent theming and dynamic UI effects across the application.

components/theme-toggle.tsx

@@ -0,0 +1,44 @@
+"use client";
+
+import { Moon, Sun, Monitor } from "lucide-react";
+import { useTheme } from "next-themes";
+import { Button } from "@/components/ui/button";
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "@/components/ui/dropdown-menu";
+import { useTranslations } from "next-intl";
+
+export function ThemeToggle() {
+  const { setTheme, theme } = useTheme();
+  const t = useTranslations("header.theme");
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="outline" size="icon">
+          <Sun className="h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
+          <Moon className="absolute h-[1.2rem] w-[1.2rem] 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="mr-2 h-4 w-4" />
+          <span>{t("light")}</span>
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("dark")}>
+          <Moon className="mr-2 h-4 w-4" />
+          <span>{t("dark")}</span>
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("system")}>
+          <Monitor className="mr-2 h-4 w-4" />
+          <span>{t("system")}</span>
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}
+