fix(downloads): Facebook files get their upload date, non-Latin names their letters

Since 2026-10-28 the signed-in Facebook read gives no upload date, so
every Facebook file since was named 0000-00-00 in Season_0 (31 on prod,
none before). The signed-out read that already titles these downloads
carries the date, so it now lends that too when the signed-in read has
none (backfill.public_title_info is now public_page_info).

On-disk names dropped every letter outside the Latin script, so a Hebrew,
Cyrillic, Greek or CJK uploader went to one shared "untitled" folder
(prod asset 503). anyascii now writes them in Latin letters
(Сергей Иванов -> Sergei_Ivanov); Latin and accented names are unchanged.

backend/app/downloads/adapters.py

@@ -227,7 +227,7 @@ class FacebookAdapter(SourceAdapter):
     # signed-out read titles the page with that same text behind the engagement counts, cut short.
     # Measured (2026-11-01, yt-dlp 2026.08.19): since 2026-10-28 every signed-in reel read gives
     # "Facebook" and NO description, while a signed-out read of the same reel still carries the text —
-    # so a placeholder left with nothing behind it gets one signed-out read (`backfill.public_title_info`).
+    # so a placeholder left with nothing behind it gets one signed-out read (`backfill.public_page_info`).
     _PLACEHOLDER_TITLES = frozenset({"video", "facebook"})
 
     def is_placeholder_title(self, title: str | None) -> bool: