feat: add checkpoint metadata to EXIF recipe data

Add support for storing checkpoint information in image EXIF metadata. The checkpoint data is simplified and includes fields like model ID, version, name, hash, and base model. This allows for better tracking of AI model checkpoints used in image generation workflows.

tests/utils/test_exif_utils.py

@@ -0,0 +1,61 @@
+import json
+
+from py.utils.exif_utils import ExifUtils
+
+
+def test_append_recipe_metadata_includes_checkpoint(monkeypatch, tmp_path):
+    captured = {}
+
+    monkeypatch.setattr(
+        ExifUtils, "extract_image_metadata", staticmethod(lambda _path: None)
+    )
+
+    def fake_update_image_metadata(image_path, metadata):
+        captured["path"] = image_path
+        captured["metadata"] = metadata
+        return image_path
+
+    monkeypatch.setattr(
+        ExifUtils, "update_image_metadata", staticmethod(fake_update_image_metadata)
+    )
+
+    checkpoint = {
+        "type": "checkpoint",
+        "modelId": 827184,
+        "modelVersionId": 2167369,
+        "modelName": "WAI-illustrious-SDXL",
+        "modelVersionName": "v15.0",
+        "hash": "ABC123",
+        "file_name": "WAI-illustrious-SDXL",
+        "baseModel": "Illustrious",
+    }
+
+    recipe_data = {
+        "title": "Semi-realism",
+        "base_model": "Illustrious",
+        "loras": [],
+        "tags": [],
+        "checkpoint": checkpoint,
+    }
+
+    image_path = tmp_path / "image.webp"
+    image_path.write_bytes(b"")
+
+    ExifUtils.append_recipe_metadata(str(image_path), recipe_data)
+
+    assert captured["path"] == str(image_path)
+    assert captured["metadata"].startswith("Recipe metadata: ")
+
+    payload = json.loads(captured["metadata"].split("Recipe metadata: ", 1)[1])
+
+    assert payload["checkpoint"] == {
+        "type": "checkpoint",
+        "modelId": 827184,
+        "modelVersionId": 2167369,
+        "modelName": "WAI-illustrious-SDXL",
+        "modelVersionName": "v15.0",
+        "hash": "abc123",
+        "file_name": "WAI-illustrious-SDXL",
+        "baseModel": "Illustrious",
+    }
+    assert payload["base_model"] == "Illustrious"