fix(ui): split editor usable without JS, untrack prop snapshots, clean orphan photo on conflict

fix(ui): explicit payer choice, validated settle-up prefill, sticky delete confirm, degraded balances

fix(ui): shared safe-next validation, no lockout on success, logout origin check, tab/feed polish

feat(ui): add settlement create, detail, edit and delete

feat(ui): add expense form with live split editor and photo upload

feat(ui): add layout, tab bar, login and logout