feat(dashboard): header user dropdown (Syncfusion) + proper logout; docs: clarify architecture; build: add splitbuttons; bump alpha.10

Dashboard

Add top-right user dropdown using Syncfusion DropDownButton: shows username + role; menu entries “Profil” and “Abmelden”.
Replace custom dropdown logic with Syncfusion component; position at header’s right edge.
Update /logout page to call backend logout and redirect to /login (reliable user switching).
Build/Config

Add @syncfusion/ej2-react-splitbuttons and @syncfusion/ej2-splitbuttons dependencies.
Update Vite optimizeDeps.include to pre-bundle splitbuttons and avoid import-analysis errors.
Docs

README: Rework Architecture Overview with clearer data flow:
Listener consumes MQTT (discovery/heartbeats) and updates API.
Scheduler reads from API and publishes events via MQTT to clients.
Clients send via MQTT and receive via MQTT.
Worker receives commands directly from API and reports results back (no MQTT).
Explicit note: MariaDB is accessed exclusively by the API Server; Dashboard never talks to DB directly.
README: Add SplitButtons to “Syncfusion Components Used”; add troubleshooting steps for @syncfusion/ej2-react-splitbuttons import issues (optimizeDeps + volume reset).
Copilot instructions: Document header user menu and splitbuttons technical notes (deps, optimizeDeps, dev-container node_modules volume).
Program info

Bump to 2025.1.0-alpha.10 with changelog:
UI: Header user menu (DropDownButton with username/role; Profil/Abmelden).
Frontend: Syncfusion SplitButtons integration + Vite pre-bundling config.
Fix: Added README guidance for splitbuttons import errors.
No breaking changes.

server/routes/clients.py

@@ -1,6 +1,7 @@
 from server.database import Session
 from models.models import Client, ClientGroup
 from flask import Blueprint, request, jsonify
+from server.permissions import admin_or_higher
 from server.mqtt_helper import publish_client_group, delete_client_group_message, publish_multiple_client_groups
 import sys
 sys.path.append('/workspace')
@@ -9,6 +10,7 @@ clients_bp = Blueprint("clients", __name__, url_prefix="/api/clients")
 
 
 @clients_bp.route("/sync-all-groups", methods=["POST"])
+@admin_or_higher
 def sync_all_client_groups():
     """
     Administrative Route: Synchronisiert alle bestehenden Client-Gruppenzuordnungen mit MQTT
@@ -73,6 +75,7 @@ def get_clients_without_description():
 
 
 @clients_bp.route("/<uuid>/description", methods=["PUT"])
+@admin_or_higher
 def set_client_description(uuid):
     data = request.get_json()
     description = data.get("description", "").strip()
@@ -127,6 +130,7 @@ def get_clients():
 
 
 @clients_bp.route("/group", methods=["PUT"])
+@admin_or_higher
 def update_clients_group():
     data = request.get_json()
     client_ids = data.get("client_ids", [])
@@ -178,6 +182,7 @@ def update_clients_group():
 
 
 @clients_bp.route("/<uuid>", methods=["PATCH"])
+@admin_or_higher
 def update_client(uuid):
     data = request.get_json()
     session = Session()
@@ -234,6 +239,7 @@ def get_clients_with_alive_status():
 
 
 @clients_bp.route("/<uuid>/restart", methods=["POST"])
+@admin_or_higher
 def restart_client(uuid):
     """
     Route to restart a specific client by UUID.
@@ -268,6 +274,7 @@ def restart_client(uuid):
 
 
 @clients_bp.route("/<uuid>", methods=["DELETE"])
+@admin_or_higher
 def delete_client(uuid):
     session = Session()
     client = session.query(Client).filter_by(uuid=uuid).first()