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.

internal/store/postgresstore.go

@@ -214,10 +214,18 @@ func (s *PostgresStore) Save(ctx context.Context, auth *cliproxyauth.Auth) (stri
 
 	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.(interface{ SetMetadata(map[string]any) }); ok {
+			setter.SetMetadata(auth.Metadata)
+		}
 		if err = auth.Storage.SaveTokenToFile(path); err != nil {
 			return "", err
 		}
 	case auth.Metadata != nil:
+		auth.Metadata["disabled"] = auth.Disabled
 		raw, errMarshal := json.Marshal(auth.Metadata)
 		if errMarshal != nil {
 			return "", fmt.Errorf("postgres store: marshal metadata: %w", errMarshal)