fix(sync): bump updated_at on set-icon + folder-delete reassignment

Both UPDATEs mutated a synced column without touching updated_at, so the
change rode in the sync snapshot but other devices skipped it (last-write-
wins saw "not newer"). Now both SET updated_at = datetime('now') (UTC).

- POST /entries/{id}/icon (PM.Handler.Entries)
- folder delete → entries reassigned to 'All' (PM.Handler.Folders)

accessed_at stays exempt (read timestamp, not synced); bulk "clear all
icons" stays exempt (device-local favicon cache purge). Invariant documented
in CLAUDE.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

delphi-backend/Handlers/PM.Handler.Entries.pas

@@ -883,7 +883,10 @@ begin
     try
       LQ.Connection := DB.Connection;
       LQ.SQL.Text :=
-        'UPDATE vault_entries SET icon_b64 = :ic ' +
+        // Bump updated_at (UTC) so the icon change wins last-write-wins on
+        // sync — without it the new icon_b64 rides in the snapshot but other
+        // devices skip it (timestamp unchanged → "not newer").
+        'UPDATE vault_entries SET icon_b64 = :ic, updated_at = datetime(''now'') ' +
         'WHERE id=:id AND user_id=:uid';
       LQ.ParamByName('ic').DataType := ftMemo;  // long text → ftMemo on SQLite
       if LIcon = '' then LQ.ParamByName('ic').Clear