feat(seo): upgrade site metadata, schema, and crawl files for OpenFrame rebrand

- update title/description to Open Source Video Review Platform
- add centralized SEO config with canonical URL + meta image (/meta.webp)
- add Open Graph and Twitter card metadata
- add JSON-LD Organization/WebSite structured data
- add robots.txt, sitemap.xml, and web app manifest routes
- version icon metadata to help search engines refresh branding

app/manifest.ts

@@ -0,0 +1,22 @@
+import type { MetadataRoute } from 'next';
+import { seoConfig } from '@/lib/seo';
+
+export default function manifest(): MetadataRoute.Manifest {
+  return {
+    name: `${seoConfig.name} - ${seoConfig.title}`,
+    short_name: seoConfig.name,
+    description: seoConfig.description,
+    start_url: '/',
+    display: 'standalone',
+    background_color: '#0a0a0a',
+    theme_color: '#0a0a0a',
+    icons: [
+      {
+        src: seoConfig.logo,
+        sizes: 'any',
+        type: 'image/svg+xml',
+        purpose: 'any',
+      },
+    ],
+  };
+}