Add model catalog with specifications for DA3 and MoGe-2 models

- Introduced ModelSpec dataclass to define model attributes.
- Added multiple models including DA3 Small, Base, Giant 1.1, Nested Giant Large 1.1, and MoGe-2 variants.
- Implemented functions to retrieve model details and metadata.
- Included BEN2 model specifications for background removal.

src/snapform/server/model_manager.py

@@ -3,7 +3,7 @@ import time
 from pathlib import Path
 from types import SimpleNamespace
 
-from . import model_catalog
+import model_catalog
 from .model_download import download_model
 
 
@@ -157,11 +157,28 @@ class ModelManager:
         self.sessions.close()
 
     def download(self, context, model_key):
+        return self._download(context, model_key, context.progress)
+
+    def download_missing(self, context, model_keys):
+        missing = [key for key in model_keys if not self.ready(key)]
+        if not missing:
+            context.progress(1.0, "Required models are ready")
+            return {"downloaded": []}
+
+        total = len(missing)
+        for index, model_key in enumerate(missing):
+            def report(value, message, *, offset=index):
+                context.progress((offset + value) / total, message)
+
+            self._download(context, model_key, report)
+        return {"downloaded": missing}
+
+    def _download(self, context, model_key, progress):
         model = model_catalog.get_downloadable_model(model_key)
         args = SimpleNamespace(
             repository=model.repository,
             model_dir=str(self.directory(model_key)),
-            progress=context.progress,
+            progress=progress,
             cancel_check=context.check_cancelled,
             label=model.label,
             allow_pattern=list(model.download_patterns),