chore: Frontend-Seiten in Komponenten/Hooks aufteilen

admin/page.tsx (1019→446), search/page.tsx (871→304), imap/page.tsx
(738→142), settings/page.tsx (641→56). Reine Umstrukturierung,
keine Verhaltensänderung, Build verifiziert.

src/hooks/useSystemInfo.ts

@@ -0,0 +1,29 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { getSystemInfo, type SystemInfo } from "@/lib/api";
+
+export function useSystemInfo() {
+  const [systemInfo, setSystemInfo] = useState<SystemInfo | null>(null);
+  const [systemInfoLoading, setSystemInfoLoading] = useState(true);
+
+  useEffect(() => {
+    let cancelled = false;
+    setSystemInfoLoading(true);
+    getSystemInfo()
+      .then((info) => {
+        if (!cancelled) setSystemInfo(info);
+      })
+      .catch(() => {
+        if (!cancelled) setSystemInfo(null);
+      })
+      .finally(() => {
+        if (!cancelled) setSystemInfoLoading(false);
+      });
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
+  return { systemInfo, systemInfoLoading };
+}