feat(usager): improve passenger form schedules, tabs, and save guards
- Prevent duplicate passenger creation on double-click save via in-flight save guard (tryBeginSave/releaseSave) and sanitized create payloads
- Warn when linking representatives already attached to another passenger (duplicate representative flow — further review planned)
- Establishment days: preselect only establishment open days on first selection; preserve manually added transport days after save/consult (approach A)
- Sync establishment day grid from schedule tab when times are entered for a day/period not yet selected (Horaires → Jours); never remove days when clearing times
- Push HeuresParJourSelector merged defaults (07:00–19:00) to form state when the user does not edit hours, so validation passes and add works without manual