Convert medical-centre landing to React + Tailwind v4 with amoCRM lead capture

Ports the single-file MedCsFiz page — the medical centre that already runs
physiotherapy and wants the existing room to earn more — to the same
architecture as the fitness and hotel landings: Vite + React 19 + TypeScript +
Tailwind v4 on the client, Express 5 for the API, zod schema shared between the
two.

The original stays in legacy/index.html as the visual reference. Its 4 MB of
inlined CSS, JS and base64 images become 12 asset files (664 KB) plus a bundle
loaded on demand; the two 1.5 MB / 750 KB device PNGs are recompressed to webp.
The page is split into 18 components with all copy moved to src/data/content.ts.

Leads reuse the fitness amoCRM integration: contact lookup by phone in every
Russian spelling, deal in the first stage of pipeline 10980758, account fields
matched automatically with the rest written to a note. Rate limit, honeypot and
a localStorage fallback so a lead survives the CRM being down. Endpoint is
/api/leads/medical-centers-existing-physio; Vite runs on 5173 and the API on
3000.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

medcenter/src/hooks/useReveal.ts

@@ -0,0 +1,32 @@
+import { useEffect, useRef, useState } from 'react'
+
+/**
+ * Scroll-in animation, matching the original page: fires once at 12% visibility
+ * and then stops observing. The `.reveal` / `.is-visible` pair lives in CSS so
+ * that `prefers-reduced-motion` can neutralise it in one place.
+ */
+export function useReveal<T extends HTMLElement = HTMLDivElement>() {
+  const ref = useRef<T>(null)
+  const [visible, setVisible] = useState(false)
+
+  useEffect(() => {
+    const element = ref.current
+    if (!element || visible) return
+
+    const observer = new IntersectionObserver(
+      (entries) => {
+        for (const entry of entries) {
+          if (!entry.isIntersecting) continue
+          setVisible(true)
+          observer.unobserve(entry.target)
+        }
+      },
+      { threshold: 0.12 },
+    )
+
+    observer.observe(element)
+    return () => observer.disconnect()
+  }, [visible])
+
+  return { ref, visible, revealClass: visible ? 'reveal is-visible' : 'reveal' }
+}