feat(auth): add support for persisting disabled flag in token storage

- Updated `FileTokenStore` and related stores (`objectstore`, `gitstore`, `postgresstore`) to include the `disabled` flag in metadata for token storage.
- Adjusted `Auth` metadata handling to initialize empty maps when absent.
- Refined logic in `auto_refresh_loop` and `conductor` to exclude `disabled` tokens from refresh checks.
- Added comprehensive unit tests to verify proper handling of the `disabled` flag in storage and retrieval operations.

sdk/auth/filestore.go

@@ -72,6 +72,10 @@ func (s *FileTokenStore) Save(ctx context.Context, auth *cliproxyauth.Auth) (str
 
 	switch {
 	case auth.Storage != nil:
+		if auth.Metadata == nil {
+			auth.Metadata = make(map[string]any)
+		}
+		auth.Metadata["disabled"] = auth.Disabled
 		if setter, ok := auth.Storage.(metadataSetter); ok {
 			setter.SetMetadata(auth.Metadata)
 		}