fix: notes over 2 MB open empty and cannot be edited (#33618)

A note over 2 MB, which one pasted screenshot can reach because images are embedded in the note, opened as an empty page and discarded what you typed. Live editing of notes had its own 2 MB limit, smaller than what the server accepts in one transfer, so it refused to load such notes. That limit now matches the server's 16 MB transfer limit, so any note the server can receive opens and saves again.

Fixes #33606

backend/open_webui/socket/utils.py

@@ -247,7 +247,8 @@ class CachedRedisDict(RedisDict):
 class YdocManager:
     COMPACTION_THRESHOLD = 500
     MAX_DOCUMENTS_PER_SESSION = 20
-    MAX_DOCUMENT_SIZE = 2 * 1024 * 1024
+    # Never below what one socket message can carry, or large notes open empty
+    MAX_DOCUMENT_SIZE = 16 * 1024 * 1024
 
     def __init__(
         self,