feat: favicon, webmanifest, og-default, improved SEO metadata + twitter cards + canonical

public/favicon.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <rect width="32" height="32" rx="8" fill="#10b981"/>
+  <text x="16" y="23" font-family="Inter,Arial,sans-serif" font-size="18" font-weight="800" text-anchor="middle" fill="white" letter-spacing="-1">Z</text>
+</svg>

public/site.webmanifest

@@ -0,0 +1,13 @@
+{
+  "name": "ZeroPost",
+  "short_name": "ZeroPost",
+  "description": "Практические материалы про ИИ",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#fafaf9",
+  "theme_color": "#10b981",
+  "icons": [
+    { "src": "/icon-192.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "/icon-512.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}