feat: migrate to Next.js 15 App Router with i18n and multi-page SEO

- Replace Vite+React SPA with Next.js 15, TypeScript, App Router
- Static export (output: 'export'), deploy via npm run deploy
- i18n routing: /ru/... and /en/... with generateStaticParams
- New pages: /uslugi/ (catalog), /uslugi/[slug]/ (8 service pages), /faq/, /kontakty/
- SEO: generateMetadata on all pages, JSON-LD Service schema, hreflang alternates
- ContactForm: 'use client', Turnstile + POST to /api/contact.php
- Fonts: Manrope via next/font/google (CSS variable)
- Remove: vite.config.js, entry-server.jsx, prerender scripts, LanguageContext

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

package.json

@@ -1,26 +1,26 @@
 {
   "name": "sag24-website",
   "private": true,
-  "version": "1.0.0",
-  "type": "module",
+  "version": "2.0.0",
   "scripts": {
-    "dev": "vite",
-    "build": "vite build && vite build --ssr src/entry-server.jsx --outDir dist/server && node scripts/prerender.mjs",
-    "deploy": "BUILD_DIR=../public_html vite build && vite build --ssr src/entry-server.jsx --outDir dist/server && BUILD_DIR=../public_html node scripts/prerender.mjs",
-    "preview": "vite preview"
+    "dev": "next dev",
+    "build": "next build",
+    "start": "next start",
+    "deploy": "BUILD_DIR=../public_html next build"
   },
   "dependencies": {
-    "@fontsource/manrope": "^5.2.8",
-    "lucide-react": "^0.263.1",
-    "react": "^18.2.0",
-    "react-dom": "^18.2.0"
+    "next": "^15.2.3",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "lucide-react": "^0.263.1"
   },
   "devDependencies": {
-    "@vitejs/plugin-react": "^4.0.0",
+    "@types/node": "^22",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "typescript": "^5",
     "autoprefixer": "^10.4.14",
     "postcss": "^8.4.24",
-    "sharp": "^0.34.5",
-    "tailwindcss": "^3.3.2",
-    "vite": "^4.4.0"
+    "tailwindcss": "^3.3.2"
   }
 }