feat: continue roadmap acceptance work

apps/api/app/media_catalog.py

@@ -49,12 +49,26 @@ def published_file(digest: str) -> tuple[Path, str] | None:
         return None
     manifest = json.loads((MEDIA_ROOT / "manifest.json").read_text(encoding="utf-8"))
     item = next((row for row in manifest.get("assets", []) if row.get("status") == "approved" and row.get("sha256") == digest), None)
-    if not item:
+    media_type = None
+    local_path = None
+    if item:
+        media_type = item.get("content_type")
+        local_path = item.get("local_path")
+    else:
+        for row in manifest.get("assets", []):
+            if row.get("status") != "approved":
+                continue
+            variant = next((candidate for candidate in row.get("derivatives", []) if candidate.get("sha256") == digest), None)
+            if variant:
+                media_type = variant.get("content_type")
+                local_path = variant.get("local_path")
+                break
+    if not local_path:
         return None
-    target = (MEDIA_ROOT / item["local_path"]).resolve()
+    target = (MEDIA_ROOT / local_path).resolve()
     if not target.is_relative_to(MEDIA_ROOT.resolve()) or not target.is_file():
         return None
-    return target, str(item["content_type"])
+    return target, str(media_type or "application/octet-stream")
 
 
 def review_assets(entity_type: str | None = None, status: str | None = None) -> list[dict]: