Add video showcase section and tighten hero-to-video spacing.

Embed VK Video demo between audience and benefits blocks, with RU/EN copy and a fallback link. Reduce vertical padding by 30% between hero, audience, and video sections.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/data/siteContent.ts

@@ -10,6 +10,12 @@ export const SITE_LINKS = {
   support: "mailto:fontosh.ivan@gmail.com",
 } as const;
 
+/** VK Video showcase — https://vkvideo.ru/video-238917656_456239017 */
+export const SHOWCASE_VIDEO = {
+  pageUrl: "https://vkvideo.ru/video-238917656_456239017",
+  embedUrl: "https://vk.com/video_ext.php?oid=-238917656&id=456239017&hd=2",
+} as const;
+
 /** Same feed as electron-builder `publish.url` in dnd_player/package.json */
 export const UPDATE_FEED_BASE = "https://updates.mailib.ru/";