feat: email change UI, Swagger UI improvements, key recovery link on landing page

- Email change modal: API key + new email → verification code → confirmed
- Swagger UI with proper OpenAPI spec (public/openapi.json + swagger-ui assets)
- Key recovery link prominently on landing page hero section
- Footer link for email change
- Updated docs.html to use swagger-ui bundle

package.json

@@ -17,7 +17,8 @@
     "nanoid": "^5.0.0",
     "nodemailer": "^8.0.1",
     "puppeteer": "^24.0.0",
-    "stripe": "^20.3.1"
+    "stripe": "^20.3.1",
+    "swagger-ui-dist": "^5.31.0"
   },
   "devDependencies": {
     "@types/express": "^5.0.0",