feat: integrate payload cms to landing page (#25)

* feat: integrate payload cms to landing page

* feat: add payload configuration and update TypeScript target

* fix: update TypeScript paths for payload configuration

* refactor: update config import paths to use local payload.config

* fix: update quotation marks for testimonials to use HTML entities

* fix: include withPayload in Next.js plugins for proper configuration

.env.example

@@ -1 +1,4 @@
-VITE_API_URL=https://api.example.com
+VITE_API_URL=
+
+CMS_SECRET=
+CMS_POSTGRES_URL=