feat(nodes): add list_images endpoint

- add `list_images` endpoint at `GET api/v1/images`
- extend `ImageStorageBase` with `list()` method, implemented it for `DiskImageStorage`
- add `ImageReponse` class to for image responses, which includes urls, metadata
- add `ImageMetadata` class (basically a stub at the moment)
- uploaded images now named `"{uuid}_{timestamp}.png"`
- add `models` modules. besides separating concerns more clearly, this helps to mitigate circular dependencies
- improve thumbnail handling

invokeai/app/invocations/upscale.py

@@ -5,10 +5,10 @@ from typing import Literal, Union
 
 from pydantic import Field
 
-from ..services.image_storage import ImageType
+from invokeai.app.models.image import ImageField, ImageType
 from ..services.invocation_services import InvocationServices
 from .baseinvocation import BaseInvocation, InvocationContext
-from .image import ImageField, ImageOutput
+from .image import ImageOutput
 
 
 class UpscaleInvocation(BaseInvocation):