refactor(proxy): rebuild app.routes in one expression instead of pop()/insert()

Addresses Greptile review feedback on #38017: avoid in-place mutation
of the shared FastAPI route list. Builds the reordered route list via
unpacking and reassigns app.router.routes wholesale, rather than
popping the appended route and inserting it back in place.

litellm/proxy/pass_through_endpoints/pass_through_endpoints.py

@@ -2582,14 +2582,16 @@ class SafeRouteAdder:
         before the first such generic route, so it is matched first instead. If no
         generic provider route is registered (e.g. a minimal deployment), leave the
         route appended -- current behavior is preserved as a safe fallback.
+
+        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]
         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:
-                routes.pop()
-                routes.insert(index, new_route)
+                app.router.routes = [*routes[:index], new_route, *routes[index:-1]]
                 return
 
     @staticmethod