fix: add /user/bulk_update to management_routes so proxy admins can access it

/user/bulk_update was missing from the management_routes list in _types.py,
causing it to fall through to a 403 in non_proxy_admin_allowed_routes_check
even for proxy admin users. Also added it to the PROXY_ADMIN_VIEW_ONLY
blocked write operations list in route_checks.py to prevent view-only
admins from using it.

litellm/proxy/_types.py

@@ -525,6 +525,7 @@ class LiteLLMRoutes(enum.Enum):
         # user
         "/user/new",
         "/user/update",
+        "/user/bulk_update",
         "/user/delete",
         "/user/info",
         "/user/list",

litellm/proxy/auth/route_checks.py

@@ -629,6 +629,7 @@ class RouteChecks:
                 in [
                     "/user/new",
                     "/user/delete",
+                    "/user/bulk_update",
                     "/team/new",
                     "/team/update",
                     "/team/delete",