L6 Benachrichtigungen & Audit: Glocke, Posteingang, Nutzer-Einstellungen, Mailkonfiguration

- Glocke im Backoffice-Header (ungelesen-Zähler, letzte 10, alle gelesen), mobil
  einbindbar über variant="mobile".
- /notifications mit Filter gelesen/ungelesen/Art, Öffnen markiert gelesen (nur
  relative Links), Pagination.
- /account Abschnitt Benachrichtigungen: E-Mail-Opt-out je Typ, Notdienst Pflicht.
- /settings/email (tenant:manage): Absendername, Antwortadresse, Empfänger Notdienst
  und Abrechnung; Validierung gegen Header-Injection, max. 20 Adressen, Audit.
- Actions unter actions/notifications mit moduleGuard + guard; Navigation ergänzt.

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

src/app/(app)/settings/email/layout.tsx

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+import { requireModule } from "@/server/modules";
+
+/** Tenant mail settings belong to the "notifications" module (actions use its moduleGuard). */
+export default async function MailSettingsLayout({ children }: Readonly<{ children: React.ReactNode }>) {
+  await requireModule("notifications");
+  return <>{children}</>;
+}

src/app/(app)/settings/email/page.tsx

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+import Link from "next/link";
+import { redirect } from "next/navigation";
+import { ArrowLeft } from "lucide-react";
+import { getTranslations } from "next-intl/server";
+import { PageHead } from "@/components/mockup-ui";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import { getMailConfig } from "@/server/mail/config";
+import { saveMailSettings } from "@/server/actions/notifications/mail-settings";
+import { getMailSettings } from "@/server/services/notifications/mail-settings";
+import { pageCtx } from "@/server/services/notifications/page-ctx";
+
+const areaCls = "min-h-28 w-full rounded-md border border-input bg-transparent px-3 py-2 font-mono text-sm";
+
+export default async function MailSettingsPage({ searchParams }: { searchParams: Promise<{ saved?: string; error?: string }> }) {
+  const ctx = await pageCtx();
+  if (!ctx.permissions.has("tenant:manage")) redirect("/dashboard");
+  const [sp, s, t] = await Promise.all([searchParams, getMailSettings(ctx), getTranslations("notifications")]);
+  const platformFrom = getMailConfig().config?.from ?? "—";
+
+  return (
+    <main className="flex-1 p-4 md:p-6">
+      <Link href="/settings" className="inline-flex min-h-11 items-center gap-1.5 text-[12.5px] font-semibold text-muted-foreground hover:text-foreground">
+        <ArrowLeft className="size-4" aria-hidden /> {t("mailSettings.back")}
+      </Link>
+      <PageHead crumb={t("mailSettings.crumb")} title={t("mailSettings.title")} sub={t("mailSettings.sub")} />
+
+      {sp.saved && (
+        <p role="status" className="mb-4 rounded-lg border border-[var(--ok)] bg-card px-4 py-3 text-sm text-[var(--ok)]">
+          ✓ {t("mailSettings.saved")}
+        </p>
+      )}
+      {sp.error && (
+        <p role="alert" className="mb-4 rounded-lg border border-[var(--risk)] bg-card px-4 py-3 text-sm text-[var(--risk)]">
+          ⚠ {t("mailSettings.invalid", { detail: sp.error.split(",").map((f) => t.has(`mailSettings.${f}`) ? t(`mailSettings.${f}`) : f).join(", ") })}
+        </p>
+      )}
+
+      <form action={saveMailSettings} className="grid max-w-4xl gap-5 lg:grid-cols-2">
+        <section className="shadow-card rounded-xl border bg-card p-5">
+          <h2 className="mb-3 font-heading text-sm font-semibold">{t("mailSettings.sender")}</h2>
+          <div className="space-y-4">
+            <div>
+              <Label htmlFor="mailFromName">{t("mailSettings.fromName")}</Label>
+              <Input id="mailFromName" name="mailFromName" maxLength={100} defaultValue={s.mailFromName ?? ""} placeholder={s.orgName ?? ""} className="mt-1 h-11" />
+              <p className="mt-1 text-[11.5px] text-muted-foreground">{t("mailSettings.fromNameHint")}</p>
+            </div>
+            <div>
+              <Label>{t("mailSettings.fromAddress")}</Label>
+              <p className="mt-1 text-[11.5px] text-muted-foreground">{t("mailSettings.fromAddressHint", { address: platformFrom })}</p>
+            </div>
+            <div>
+              <Label htmlFor="mailReplyTo">{t("mailSettings.replyTo")}</Label>
+              <Input id="mailReplyTo" name="mailReplyTo" type="email" defaultValue={s.mailReplyTo ?? ""} className="mt-1 h-11" />
+              <p className="mt-1 text-[11.5px] text-muted-foreground">{t("mailSettings.replyToHint")}</p>
+            </div>
+          </div>
+        </section>
+
+        <section className="shadow-card rounded-xl border bg-card p-5">
+          <h2 className="mb-3 font-heading text-sm font-semibold">{t("mailSettings.recipients")}</h2>
+          <div className="space-y-4">
+            <div>
+              <Label htmlFor="emergencyRecipients">{t("mailSettings.emergencyRecipients")}</Label>
+              <textarea id="emergencyRecipients" name="emergencyRecipients" defaultValue={s.emergencyRecipients.join("\n")} className={`${areaCls} mt-1`} />
+              <p className="mt-1 text-[11.5px] text-muted-foreground">{t("mailSettings.emergencyHint")}</p>
+            </div>
+            <div>
+              <Label htmlFor="billingRecipients">{t("mailSettings.billingRecipients")}</Label>
+              <textarea id="billingRecipients" name="billingRecipients" defaultValue={s.billingRecipients.join("\n")} className={`${areaCls} mt-1`} />
+              <p className="mt-1 text-[11.5px] text-muted-foreground">{t("mailSettings.billingHint")}</p>
+            </div>
+          </div>
+        </section>
+
+        <div className="lg:col-span-2">
+          <Button type="submit" className="min-h-11">{t("mailSettings.save")}</Button>
+        </div>
+      </form>
+    </main>
+  );
+}