Initial commit: Kalendartool (Next.js, Prisma, Docker)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app/admin/calendars/page.tsx

@@ -0,0 +1,58 @@
+/**
+ * Admin: Kalenderverwaltung (Cards-Ansicht).
+ * Zeigt alle Kalender als Karten - eigene und die anderer Benutzer.
+ * Verwaltung direkt im Bearbeiten-Modal oder auf der Detailseite
+ * /admin/calendars/[id] (Invites, Mitglieder, Reservierungen).
+ */
+import { redirect } from 'next/navigation';
+import { prisma } from '@/lib/db/client';
+import { requireDbUser } from '@/lib/api/context';
+import { AppShell } from '@/components/layout/AppShell';
+import { CalendarManager } from '@/components/admin/CalendarManager';
+
+export default async function ManageCalendarsPage() {
+  const user = await requireDbUser().catch(() => null);
+  if (!user || user.role !== 'ADMIN') {
+    redirect('/dashboard');
+  }
+
+  const calendars = await prisma.calendar.findMany({
+    orderBy: { createdAt: 'desc' },
+    select: {
+      id: true,
+      title: true,
+      description: true,
+      timezone: true,
+      isActive: true,
+      maxReservationMinutes: true,
+      showTitleToMembers: true,
+      showNotesToMembers: true,
+      ownerId: true,
+      owner: { select: { email: true, username: true } },
+      _count: { select: { members: true, reservations: true } },
+    },
+  });
+
+  return (
+    <AppShell role={user.role} userEmail={user.email} username={user.username}>
+      <CalendarManager
+        currentUserId={user.id}
+        isAdmin={user.role === 'ADMIN'}
+        initialCalendars={calendars.map((calendar) => ({
+          id: calendar.id,
+          title: calendar.title,
+          description: calendar.description,
+          timezone: calendar.timezone,
+          isActive: calendar.isActive,
+          ownerEmail: calendar.owner.username ?? calendar.owner.email,
+          isOwn: calendar.ownerId === user.id,
+          memberCount: calendar._count.members,
+          reservationCount: calendar._count.reservations,
+          maxReservationMinutes: calendar.maxReservationMinutes,
+          showTitleToMembers: calendar.showTitleToMembers,
+          showNotesToMembers: calendar.showNotesToMembers,
+        }))}
+      />
+    </AppShell>
+  );
+}