fix: configure France timezone globally and align flottes date displays
- add dayjs UTC/timezone plugins, set fr locale and Europe/Paris default in src/utils/format-time.ts
- introduce dayjsFR() helper with heuristic to distinguish UTC audit timestamps (4+ fractional digits) from Paris wall-clock user inputs
- route formatDate/formatDateTime/formatTime/formatSmartDatetime through dayjsFR
- import format-time at app root and set html lang=fr
- replace direct dayjs().format(), date-fns format(new Date()), toLocaleDateString() and manual ISO parsing with central formatters across flottes (fuel anomaly, kilometrage, documents, revision, vehicle row)
Closes VSN-2691