feat: complete user management system

- Add UserProfile role field (superadmin/admin/trainer)
- Create role-based permission classes
- Implement UserManagementViewSet with CRUD
- Add frontend types and components
- Create users management page
- Add sidebar navigation for users
- Only superadmins can manage users

frontend/src/app/(dashboard)/settings/users/page.tsx

@@ -0,0 +1,214 @@
+"use client"
+
+import { useEffect, useState } from "react"
+import { useAuth } from "@/lib/auth"
+import { apiFetch, IUser, ICreateUserInput, IUpdateUserInput } from "@/lib/api"
+import { Button } from "@/components/ui/button"
+import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card"
+import { Badge } from "@/components/ui/badge"
+import {
+  Table,
+  TableBody,
+  TableCell,
+  TableHead,
+  TableHeader,
+  TableRow,
+} from "@/components/ui/table"
+import { Plus, Pencil, Trash2, Key } from "lucide-react"
+import { toast } from "sonner"
+import { UserForm } from "@/components/users/user-form"
+import { FadeIn } from "@/components/animations"
+
+const roleColors: Record<string, string> = {
+  superadmin: 'bg-red-100 text-red-800',
+  admin: 'bg-blue-100 text-blue-800',
+  trainer: 'bg-green-100 text-green-800',
+}
+
+const roleLabels: Record<string, string> = {
+  superadmin: 'Super Admin',
+  admin: 'Admin',
+  trainer: 'Trainer',
+}
+
+export default function UsersPage() {
+  const { token } = useAuth()
+  const [users, setUsers] = useState<IUser[]>([])
+  const [loading, setLoading] = useState(true)
+  const [isFormOpen, setIsFormOpen] = useState(false)
+  const [editingUser, setEditingUser] = useState<IUser | null>(null)
+  const [formMode, setFormMode] = useState<'create' | 'edit'>('create')
+
+  const fetchUsers = async () => {
+    try {
+      const data = await apiFetch<IUser[]>('/auth/users/', { token: token! })
+      setUsers(data)
+    } catch {
+      toast.error('Fehler beim Laden der Benutzer')
+    } finally {
+      setLoading(false)
+    }
+  }
+
+  useEffect(() => {
+    fetchUsers()
+  }, [token])
+
+  const handleCreate = async (data: ICreateUserInput) => {
+    try {
+      await apiFetch<IUser>('/auth/users/', {
+        method: 'POST',
+        token: token!,
+        body: JSON.stringify(data),
+      })
+      toast.success('Benutzer erstellt')
+      fetchUsers()
+    } catch {
+      toast.error('Fehler beim Erstellen')
+    }
+  }
+
+  const handleUpdate = async (data: IUpdateUserInput) => {
+    if (!editingUser) return
+    try {
+      await apiFetch<IUser>(`/auth/users/${editingUser.id}/`, {
+        method: 'PATCH',
+        token: token!,
+        body: JSON.stringify(data),
+      })
+      toast.success('Benutzer aktualisiert')
+      fetchUsers()
+    } catch {
+      toast.error('Fehler beim Aktualisieren')
+    }
+  }
+
+  const handleDelete = async (id: number) => {
+    if (!confirm('Bist du sicher?')) return
+    try {
+      await apiFetch(`/auth/users/${id}/`, {
+        method: 'DELETE',
+        token: token!,
+      })
+      toast.success('Benutzer gelöscht')
+      fetchUsers()
+    } catch {
+      toast.error('Fehler beim Löschen')
+    }
+  }
+
+  const handlePasswordReset = async (user: IUser) => {
+    const password = prompt(`Neues Passwort für ${user.username}:`)
+    if (!password) return
+    try {
+      await apiFetch(`/auth/users/${user.id}/set_password/`, {
+        method: 'POST',
+        token: token!,
+        body: JSON.stringify({ password }),
+      })
+      toast.success('Passwort geändert')
+    } catch {
+      toast.error('Fehler beim Passwort ändern')
+    }
+  }
+
+  const openCreateForm = () => {
+    setEditingUser(null)
+    setFormMode('create')
+    setIsFormOpen(true)
+  }
+
+  const openEditForm = (user: IUser) => {
+    setEditingUser(user)
+    setFormMode('edit')
+    setIsFormOpen(true)
+  }
+
+  if (loading) return <div>Laden...</div>
+
+  return (
+    <FadeIn>
+      <Card>
+        <CardHeader className="flex flex-row items-center justify-between">
+          <CardTitle>Benutzerverwaltung</CardTitle>
+          <Button onClick={openCreateForm}>
+            <Plus className="w-4 h-4 mr-2" />
+            Neuer Benutzer
+          </Button>
+        </CardHeader>
+        <CardContent>
+          <Table>
+            <TableHeader>
+              <TableRow>
+                <TableHead>Name</TableHead>
+                <TableHead>Username</TableHead>
+                <TableHead>E-Mail</TableHead>
+                <TableHead>Rolle</TableHead>
+                <TableHead>Status</TableHead>
+                <TableHead className="text-right">Aktionen</TableHead>
+              </TableRow>
+            </TableHeader>
+            <TableBody>
+              {users.map((user) => (
+                <TableRow key={user.id}>
+                  <TableCell>
+                    {user.first_name} {user.last_name}
+                  </TableCell>
+                  <TableCell>{user.username}</TableCell>
+                  <TableCell>{user.email}</TableCell>
+                  <TableCell>
+                    <Badge className={roleColors[user.role || 'trainer'] || 'bg-gray-100'}>
+                      {roleLabels[user.role || 'trainer'] || user.role}
+                    </Badge>
+                  </TableCell>
+                  <TableCell>
+                    {user.is_active ? (
+                      <span className="text-green-600">Aktiv</span>
+                    ) : (
+                      <span className="text-red-600">Inaktiv</span>
+                    )}
+                  </TableCell>
+                  <TableCell className="text-right">
+                    <div className="flex justify-end gap-2">
+                      <Button
+                        variant="ghost"
+                        size="icon"
+                        onClick={() => handlePasswordReset(user)}
+                        title="Passwort ändern"
+                      >
+                        <Key className="w-4 h-4" />
+                      </Button>
+                      <Button
+                        variant="ghost"
+                        size="icon"
+                        onClick={() => openEditForm(user)}
+                      >
+                        <Pencil className="w-4 h-4" />
+                      </Button>
+                      <Button
+                        variant="ghost"
+                        size="icon"
+                        onClick={() => handleDelete(user.id!)}
+                        className="text-red-600"
+                      >
+                        <Trash2 className="w-4 h-4" />
+                      </Button>
+                    </div>
+                  </TableCell>
+                </TableRow>
+              ))}
+            </TableBody>
+          </Table>
+        </CardContent>
+      </Card>
+
+      <UserForm
+        open={isFormOpen}
+        onOpenChange={setIsFormOpen}
+        onSubmit={formMode === 'create' ? handleCreate : handleUpdate}
+        user={editingUser || undefined}
+        mode={formMode}
+      />
+    </FadeIn>
+  )
+}

frontend/src/components/layout/Sidebar.tsx

@@ -100,6 +100,17 @@ export function Sidebar() {
             Einstellungen
           </motion.div>
         </Link>
+        <Link href="/settings/users" className="block mb-2">
+          <motion.div
+            className="flex items-center gap-3 px-3 pl-8 py-1 rounded-lg text-xs text-sidebar-foreground hover:bg-sidebar-accent hover:text-sidebar-accent-foreground"
+            whileHover={{ x: 2 }}
+            whileTap={{ scale: 0.98 }}
+            transition={{ duration: 0.15 }}
+          >
+            <Users className="w-4 h-4" />
+            Benutzer
+          </motion.div>
+        </Link>
         <div className="flex items-center justify-between px-3 py-2">
           <motion.span 
             className="text-sm text-sidebar-foreground"