Vrbo description counter should measure bytes (not characters) to prevent silent cutoffs

Hospitable's Vrbo description editor counts characters (10,000 limit), but Vrbo's API enforces bytes (10,000 limit) on the formatted string. Because we convert each line break to a
tag on push (+3 bytes per line), a description that passes our editor can silently exceed Vrbo's real limit. Vrbo drops the tail without surfacing an error, so hosts don't know their listing was truncated. Proposed solution Update the Vrbo description editor to: - Count and display bytes after normalization, not raw characters - Show a live warning as the byte count approaches 10,000 - Block save (or hard error) when over, so nothing gets silently truncated