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

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

app/api/users/route.ts

@@ -0,0 +1,42 @@
+/**
+ * GET /api/users - Benutzerverwaltung (nur ADMIN).
+ *
+ * Liefert alle Benutzer mit Rolle und Kalender-Beziehungen, damit
+ * ein Admin Rollen vergeben und Zuordnungen ueberblicken kann.
+ */
+import { NextResponse } from 'next/server';
+import { prisma } from '@/lib/db/client';
+import { requireDbUser } from '@/lib/api/context';
+import { errorResponse, forbiddenResponse } from '@/lib/api/responses';
+
+export async function GET(): Promise<NextResponse> {
+  try {
+    const user = await requireDbUser();
+    if (user.role !== 'ADMIN') {
+      return forbiddenResponse();
+    }
+
+    const users = await prisma.user.findMany({
+      orderBy: { createdAt: 'asc' },
+      select: {
+        id: true,
+        email: true,
+        username: true,
+        role: true,
+        createdAt: true,
+        memberships: {
+          select: {
+            calendar: { select: { id: true, title: true, isActive: true } },
+          },
+        },
+        ownedCalendars: {
+          select: { id: true, title: true, isActive: true },
+        },
+      },
+    });
+
+    return NextResponse.json({ users });
+  } catch (error) {
+    return errorResponse(error);
+  }
+}