feat(seo): GEO/SEO optimizations for AI search visibility

[bokiko]

🔍 GEO/SEO Optimization PR

Improves PingDiff's visibility in AI-powered search engines (ChatGPT, Claude, Perplexity, Google AI Overviews) while strengthening traditional SEO foundations.

Changes

1. llms.txt (web/public/llms.txt)

• New file following the llms.txt spec
• Describes PingDiff, supported games, server regions, tech stack
• Helps AI crawlers understand and cite the site

2. AI Crawler Rules (web/src/app/robots.ts)

• Added explicit allow rules for 9 AI crawlers: GPTBot, ClaudeBot, PerplexityBot, Google-Extended, Amazonbot, Applebot-Extended, Bytespider, CCBot, FacebookExternalHit
• /api/ still disallowed for all

3. Dynamic OG Image (web/src/app/opengraph-image.tsx)

• Replaced SVG og:image (unsupported by most platforms) with Next.js ImageResponse API
• Dark themed card with PingDiff branding, tagline, and key stats
• Auto-generated PNG at /opengraph-image

4. Schema Cleanup (web/src/app/layout.tsx)

• Removed fake aggregateRating (ratingValue: 5, ratingCount: 100) — Google penalizes fabricated ratings
• Added FAQPage JSON-LD with 5 gaming-relevant Q&As for rich snippet eligibility

5. Twitter Meta (web/src/app/layout.tsx)

• Added twitter:site and twitter:creator tags

Impact

• 🤖 AI search engines can now discover and cite PingDiff content
• 📊 FAQ schema enables rich snippets in Google search results
• 🖼️ OG image now renders correctly on Discord, Twitter, Slack, etc.
• ✅ No fake ratings = no Google penalty risk

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