fix: use _global fallback for empty ticker in MinIO storage paths

Macro news documents have no ticker, causing upload_normalized_text
and upload_parser_output to produce paths like parsed//2026/...
which MinIO rejects as XMinioInvalidObjectName. Use '_global' as
the path segment when ticker is empty, matching the existing
macro prefix pattern in upload_raw_document.

services/shared/storage.py

@@ -221,8 +221,9 @@ def upload_normalized_text(
     Stores under parsed/{ticker}/{yyyy}/{mm}/{dd}/{document_id}/normalized.txt
     """
     ts = timestamp or datetime.now(timezone.utc)
+    safe_ticker = ticker or "_global"
     path = (
-        f"parsed/{ticker}/{ts.year}/{ts.month:02d}/{ts.day:02d}/"
+        f"parsed/{safe_ticker}/{ts.year}/{ts.month:02d}/{ts.day:02d}/"
         f"{document_id}/normalized.txt"
     )
     return upload_artifact(
@@ -244,8 +245,9 @@ def upload_parser_output(
     Stores under parsed/{ticker}/{yyyy}/{mm}/{dd}/{document_id}/parser_output.json
     """
     ts = timestamp or datetime.now(timezone.utc)
+    safe_ticker = ticker or "_global"
     path = (
-        f"parsed/{ticker}/{ts.year}/{ts.month:02d}/{ts.day:02d}/"
+        f"parsed/{safe_ticker}/{ts.year}/{ts.month:02d}/{ts.day:02d}/"
         f"{document_id}/parser_output.json"
     )
     return upload_artifact(