fix(update): resolve template path when updating to a different base model (#1059)

Version-tab updates reused the current version's folder, so updating a LoRA
to a version with a different base model (e.g. Illustrious -> Anima) ignored
the download path template and landed in the old version's directory.

When the target version's base model differs from the current local version
and a path template is configured, re-resolve the template under the same
model root. The backend keeps an explicitly provided root when
use_save_dir_as_root is set, so regular downloads still use the default root.

py/services/download_coordinator.py

@@ -83,6 +83,7 @@ class DownloadCoordinator:
             save_dir=payload.get("model_root"),
             relative_path=payload.get("relative_path", ""),
             use_default_paths=payload.get("use_default_paths", False),
+            use_save_dir_as_root=payload.get("use_save_dir_as_root", False),
             progress_callback=progress_callback,
             download_id=download_id,
             source=payload.get("source"),