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/useAdminUpload.ts

@@ -0,0 +1,58 @@
+"use client";
+
+import { useState, useRef } from "react";
+import {
+  uploadMailFiles,
+  getUploadProgress,
+  type UploadJob,
+} from "@/lib/api";
+
+export function useAdminUpload() {
+  const [uploadDragging, setUploadDragging] = useState(false);
+  const [uploadJob, setUploadJob] = useState<UploadJob | null>(null);
+  const [uploadError, setUploadError] = useState("");
+  const [uploadLoading, setUploadLoading] = useState(false);
+  const uploadPollRef = useRef<ReturnType<typeof setInterval> | null>(null);
+
+  async function handleUploadFiles(files: File[]) {
+    const valid = files.filter(f => f.name.toLowerCase().endsWith(".eml") || f.name.toLowerCase().endsWith(".mbox"));
+    if (valid.length === 0) {
+      setUploadError("Nur .eml und .mbox Dateien erlaubt.");
+      return;
+    }
+    setUploadError("");
+    setUploadJob(null);
+    setUploadLoading(true);
+    try {
+      const { job_id } = await uploadMailFiles(valid);
+      const poll = setInterval(async () => {
+        try {
+          const job = await getUploadProgress(job_id);
+          setUploadJob(job);
+          if (job.status !== "running") {
+            clearInterval(poll);
+            uploadPollRef.current = null;
+            setUploadLoading(false);
+          }
+        } catch {
+          clearInterval(poll);
+          uploadPollRef.current = null;
+          setUploadLoading(false);
+        }
+      }, 1500);
+      uploadPollRef.current = poll;
+    } catch (e: unknown) {
+      setUploadError(e instanceof Error ? e.message : "Upload fehlgeschlagen.");
+      setUploadLoading(false);
+    }
+  }
+
+  return {
+    uploadDragging,
+    setUploadDragging,
+    uploadJob,
+    uploadError,
+    uploadLoading,
+    handleUploadFiles,
+  };
+}