feat: Add comprehensive SEO improvements

- Enhanced metadata with Open Graph and Twitter Card tags
- Added robots.ts for search engine crawling directives
- Added sitemap.ts for site structure
- Improved image alt text for better accessibility and SEO
- Added JSON-LD structured data (Schema.org SoftwareApplication)
- Configured proper meta tags including keywords, authors, and robots settings
- Set metadataBase for proper URL resolution

components/chat-message-display.tsx

@@ -187,7 +187,7 @@ export function ChatMessageDisplay({
                                                     src={part.url}
                                                     width={200}
                                                     height={200}
-                                                    alt={`file-${index}`}
+                                                    alt={`Uploaded diagram or image for AI analysis`}
                                                     className="rounded-md border"
                                                     style={{
                                                         objectFit: "contain",