venus-db-backup.sh: trash-fails fallback hard-deletes (rm -f) instead of degrading safely

venus-db-backup.sh delete line is: command -v trash >/dev/null && trash "$f" 2>/dev/null || rm -f "$f". Shell precedence makes rm -f run whenever trash EXISTS but FAILS — precisely the case the fallback was written to survive. A recoverable delete silently becomes an unrecoverable one, in a backup tool, on live clinical data artifacts. Found by bin-venus-cc while measuring for VENUS-350 (msimzrt929fs); out of that WI scope, filed on its own merits and bin has accepted it. Do NOT edit the script while it is evidence in VENUS-350 — hold until that WI releases the file. Fix is precedence grouping, not a rewrite. The failure-direction argument is the point: a fallback must degrade toward recoverable, never away from it.