uv {lock,sync}: propagate index URLs to registry client

Otherwise the `uv lock` command wasn't respecting the index URL option.

This is a follow-up to #3984, and I believe should now allow #3970 to be
merged.

crates/uv/src/commands/project/lock.rs

@@ -36,6 +36,8 @@ pub(crate) async fn lock(
         warn_user!("`uv lock` is experimental and may change without warning.");
     }
 
+    dbg!(&index_locations);
+
     // Find the project requirements.
     let project = ProjectWorkspace::discover(&std::env::current_dir()?, None).await?;
 
@@ -99,6 +101,7 @@ pub(super) async fn do_lock(
     // Initialize the registry client.
     // TODO(zanieb): Support client options e.g. offline, tls, etc.
     let client = RegistryClientBuilder::new(cache.clone())
+        .index_urls(index_locations.index_urls())
         .markers(markers)
         .platform(venv.interpreter().platform())
         .build();

crates/uv/src/commands/project/sync.rs

@@ -90,6 +90,7 @@ pub(super) async fn do_sync(
     // Initialize the registry client.
     // TODO(zanieb): Support client options e.g. offline, tls, etc.
     let client = RegistryClientBuilder::new(cache.clone())
+        .index_urls(index_locations.index_urls())
         .markers(markers)
         .platform(venv.interpreter().platform())
         .build();