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.

tests/test_server.py

@@ -44,6 +44,35 @@ class ServerTest(unittest.TestCase):
         self.addCleanup(self.jobs_temp.cleanup)
         self.storage_root = Path(self.jobs_temp.name)
 
+    def test_required_model_download_skips_ready_model(self):
+        manager = self.server_module.ModelManager(Path("."))
+        downloads = []
+        context = SimpleNamespace(progress=lambda *_args: None)
+        with patch.object(
+            manager,
+            "ready",
+            side_effect=lambda key: key == "BEN2_BASE",
+        ), patch.object(
+            manager,
+            "_download",
+            side_effect=lambda _context, key, _progress: downloads.append(key),
+        ):
+            result = manager.download_missing(
+                context,
+                ("MOGE2_VITS_NORMAL", "BEN2_BASE"),
+            )
+
+        self.assertEqual(downloads, ["MOGE2_VITS_NORMAL"])
+        self.assertEqual(result, {"downloaded": ["MOGE2_VITS_NORMAL"]})
+
+    def test_models_are_owned_by_the_server_resource(self):
+        self.assertFalse((PROJECT_ROOT / "src" / "snapform" / "models.py").exists())
+        with tempfile.TemporaryDirectory() as directory:
+            manager = self.server_module.ModelManager(Path(directory))
+            snapshot = manager.snapshot()
+        self.assertIn("catalog", snapshot)
+        self.assertTrue(snapshot["catalog"])
+
     def create_cache(self):
         cache = self.server_module.ModelSessionCache.__new__(
             self.server_module.ModelSessionCache
@@ -178,6 +207,7 @@ class ServerTest(unittest.TestCase):
             set(server.handlers),
             {
                 "download-model",
+                "download-required-models",
                 "remove-background",
                 "extract-frames",
                 "generate-da3-depth",