Route social media crawlers to OG API for blog posts

Adds Vercel rewrite rule to detect Twitter, Facebook, LinkedIn, Slack,
Discord, Telegram, and WhatsApp crawlers and serve them the OG API
response with proper meta tags instead of the SPA.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: MaxGhenis

app/vercel.json

@@ -1,3 +1,16 @@
 {
-  "rewrites": [{ "source": "/(.*)", "destination": "/" }]
-}
+  "rewrites": [
+    {
+      "source": "/:country(uk|us)/research/:slug",
+      "has": [
+        {
+          "type": "header",
+          "key": "user-agent",
+          "value": ".*(Twitterbot|facebookexternalhit|LinkedInBot|Slackbot|Discordbot|TelegramBot|WhatsApp).*"
+        }
+      ],
+      "destination": "/api/og?path=/:country/research/:slug"
+    },
+    { "source": "/(.*)", "destination": "/" }
+  ]
+}

social-posts.md

@@ -0,0 +1,28 @@
+# Mansion Tax Social Posts
+
+## X (Twitter) - Post 1 (with image)
+
+Where would a mansion tax hit hardest?
+
+We mapped 2024 property sales above £2m by UK constituency. Three central London seats—Cities of London & Westminster, Kensington & Bayswater, and Chelsea & Fulham—account for 21% of all high-value sales nationwide.
+
+---
+
+## X (Twitter) - Post 2 (reply with link)
+
+Explore the interactive map and toggle between £1.5m and £2m thresholds: policyengine.org/uk/research/uk-mansion-tax-autumn-budget
+
+---
+
+## LinkedIn
+
+Ahead of tomorrow's Autumn Budget, we mapped where a mansion tax would concentrate.
+
+Using Land Registry data, we identified 8,213 property sales above £2 million in 2024—just 0.9% of all transactions. The geographic concentration is stark: three central London constituencies alone account for a fifth of these sales.
+
+Key findings:
+• Raising the threshold from £1.5m to £2m nearly halves affected properties (14,820 → 8,213)
+• London constituencies account for 45-46% of high-value sales
+• The median constituency saw just 6 sales above £2m
+
+The interactive map lets you search any constituency and toggle between thresholds.