fix(proxy): satisfy the type-discipline gate for the route-reordering fix

- routes/new_route: Final, closing the LIT010 rebind-openness gap
- # mutable-ok / # rebind-ok on the app.router.routes reassignment:
  it necessarily constructs a list literal and mutates state reachable
  from the app parameter, since Starlette's own Router.routes must
  stay a real, appendable list for the framework's own route
  registration to keep working -- an immutable rewrite is not possible
  here, per CLAUDE.md's own last-resort carve-out for this case

CI failure: LIT002 total exceeded budget by the 1 new violation this
PR added (https://github.com/BerriAI/litellm/pull/38017/checks).

litellm/proxy/pass_through_endpoints/pass_through_endpoints.py

@@ -2586,12 +2586,16 @@ class SafeRouteAdder:
         Builds the reordered list in one expression and reassigns app.router.routes
         wholesale, rather than mutating the existing list in place with pop()/insert().
         """
-        routes = app.routes
-        new_route = routes[-1]
+        routes: Final = app.routes
+        new_route: Final = routes[-1]
         for index, route in enumerate(routes[:-1]):
             route_path = getattr(route, "path", None)
             if route_path and SafeRouteAdder._GENERIC_PROVIDER_PATH_MARKER in route_path:
-                app.router.routes = [*routes[:index], new_route, *routes[index:-1]]
+                app.router.routes = [  # mutable-ok: framework's list  # rebind-ok: reordering is the fix
+                    *routes[:index],
+                    new_route,
+                    *routes[index:-1],
+                ]
                 return
 
     @staticmethod