feat(pos): add config blueprint — branches, employees, theming

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pos/app.py

@@ -7,6 +7,9 @@ def create_app():
     from blueprints.auth_bp import auth_bp
     app.register_blueprint(auth_bp)
 
+    from blueprints.config_bp import config_bp
+    app.register_blueprint(config_bp)
+
     # Health check
     @app.route('/pos/health')
     def health():