fix: catch UnicodeDecodeError during manifest parsing

Catch UnicodeDecodeError alongside JSONDecodeError, suggested by copilot

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: karanw330

cosmos/dbt/graph.py

@@ -1379,7 +1379,7 @@ def _load_manifest_from_file(self, manifest_path: Path | ObjectStoragePath) -> d
                     if not content.strip():
                         raise CosmosLoadDbtException(f"Failed to load dbt manifest at `{manifest_path}`: file is empty")
                     manifest = json.loads(content)
-            except json.JSONDecodeError as e:
+            except (json.JSONDecodeError, UnicodeDecodeError) as e:
                 raise CosmosLoadDbtException(
                     f"Failed to load dbt manifest at `{manifest_path}`: file is not valid JSON ({e})"
                 ) from e