Bugfix/ignore dot directories on model scan (#4865)

## What type of PR is this? (check all applicable)

- [ ] Refactor
- [ ] Feature
- [X] Bug Fix
- [ ] Optimization
- [ ] Documentation Update
- [ ] Community Node Submission


## Have you discussed this change with the InvokeAI team?
- [X] Yes
- [ ] No, because:

      
## Have you updated all relevant documentation?
- [X] Yes
- [ ] No


## Description

Mac users have a recurring issue in which a `.DS_Store` directory is
created in their `models` hierarchy, causing the new model scanner to
freak out. This PR skips over any paths that begin with a dot. I haven't
tested it on a Macintosh, so I'm not 100% certain it will do the trick.

## Related Tickets & Documents

- Related Issue #4815 

## QA Instructions, Screenshots, Recordings

Someone with a Mac please try to reproduce the `.DS_Store` crash and
then see if applying this PR addresses the issue.

invokeai/backend/model_management/model_manager.py

@@ -986,6 +986,8 @@ class ModelManager(object):
 
                     for model_path in models_dir.iterdir():
                         if model_path not in loaded_files:  # TODO: check
+                            if model_path.name.startswith("."):
+                                continue
                             model_name = model_path.name if model_path.is_dir() else model_path.stem
                             model_key = self.create_key(model_name, cur_base_model, cur_model_type)