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/robots.ts

@@ -0,0 +1,16 @@
+import type { MetadataRoute } from 'next';
+import { seoConfig } from '@/lib/seo';
+
+export default function robots(): MetadataRoute.Robots {
+  return {
+    rules: [
+      {
+        userAgent: '*',
+        allow: '/',
+        disallow: ['/api/', '/admin', '/dashboard', '/projects', '/settings', '/workspaces'],
+      },
+    ],
+    sitemap: `${seoConfig.url}/sitemap.xml`,
+    host: seoConfig.url,
+  };
+}