[Website] Cut over to the rebuilt site (#21825)

Renaming the package so any further PRs directed to the website are
targeted to the reworked code instead of diverging. Once merged, I will
start preparing this for deployment to dev to test before releasing to
prod. Any improvements will also be applied to this package.

I avoided making significant changes to API routes so nothing breaks,
but will test it thoroughly today to confirm. That said, everything is
ported - double checked.

Big diff PR, impossible to review, but last one! No more rebuilds.

packages/twenty-website/src/ui/SectionStack.tsx

@@ -0,0 +1,20 @@
+import { styled } from '@linaria/react';
+
+import { mediaUp, spacing } from '@/tokens';
+
+// The gap between a section's intro and its content block: one value pair
+// across the site (Problem, ThreeCards, FAQ, and onward).
+export const SectionStack = styled.div`
+  display: grid;
+  grid-template-columns: 1fr;
+
+  & > * + * {
+    margin-top: ${spacing(10)};
+  }
+
+  ${mediaUp('md')} {
+    & > * + * {
+      margin-top: ${spacing(20)};
+    }
+  }
+`;