feat: BLACK HEART DANCE HOUSE landing page

Landing page with Hero, About, Team, Classes, and Contact sections.
Light/dark mode, scroll reveal animations, Yandex Maps, responsive design.
Next.js 16 + Tailwind v4 + TypeScript.

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

src/lib/constants.ts

@@ -0,0 +1,18 @@
+import type { NavLink } from "@/types";
+
+export const BRAND = {
+  name: "BLACK HEART DANCE HOUSE",
+  shortName: "Blackheart",
+  instagram: "https://instagram.com/blackheartdancehouse",
+  instagramHandle: "@blackheartdancehouse",
+} as const;
+
+export const NAV_LINKS: NavLink[] = [
+  { label: "О нас", href: "#about" },
+  { label: "Команда", href: "#team" },
+  { label: "Направления", href: "#classes" },
+  { label: "Контакты", href: "#contact" },
+];
+
+export const API_BASE_URL =
+  process.env.NEXT_PUBLIC_API_URL ?? "http://localhost:8000/api/v1";