fix(ci): handle empty changed-file lists

Use a Git diff fallback when Woodpecker provides no changed-file list.

Co-authored-by: JustMe <mr.toing@outlook.com>

ci/main-fastlane.py

@@ -39,7 +39,9 @@ def read_changed_files() -> list[str]:
         try:
             value = json.loads(raw)
             if isinstance(value, list):
-                return [str(path).replace("\\", "/") for path in value]
+                changed = [str(path).replace("\\", "/") for path in value]
+                if changed:
+                    return changed
         except json.JSONDecodeError:
             return [path.strip().replace("\\", "/") for path in raw.split(",") if path.strip()]