first commit. added CI, Docker compose, blank client and server. used unit tests, they pass

web/src/App.tsx

@@ -0,0 +1,50 @@
+import { useEffect, useState } from 'react'
+import { pingApi, type PingResponse } from './api'
+import './index.css'
+
+type ApiState =
+  | { status: 'loading' }
+  | { status: 'ok'; data: PingResponse }
+  | { status: 'error'; error: string }
+
+function App() {
+  const [api, setApi] = useState<ApiState>({ status: 'loading' })
+
+  useEffect(() => {
+    let cancelled = false
+    pingApi()
+      .then((data) => {
+        if (!cancelled) setApi({ status: 'ok', data })
+      })
+      .catch((err: unknown) => {
+        if (!cancelled) setApi({ status: 'error', error: String(err) })
+      })
+    return () => {
+      cancelled = true
+    }
+  }, [])
+
+  return (
+    <main className="shell">
+      <h1>Messenger</h1>
+      <div className="card">
+        <div className="status-row">
+          <span className={`dot ${api.status}`} aria-hidden />
+          <span className="status-label">
+            {api.status === 'loading' && 'API: connecting…'}
+            {api.status === 'ok' && 'API: connected'}
+            {api.status === 'error' && 'API: unreachable'}
+          </span>
+        </div>
+        {api.status === 'ok' && (
+          <p className="detail">
+            {api.data.message} · server time {api.data.time}
+          </p>
+        )}
+        {api.status === 'error' && <p className="detail">{api.error}</p>}
+      </div>
+    </main>
+  )
+}
+
+export default App