feat(frontend) : add date filter component to time-tracking page

Reusable DateFilter component using @vuepic/vue-datepicker with day/week
toggle. Selecting a day switches to day view, selecting a week navigates
the calendar to that week. Includes "Aujourd'hui" and "Cette semaine"
quick shortcuts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/i18n/locales/fr.json

@@ -172,7 +172,9 @@
         "dateFilter": "Date",
         "today": "Aujourd'hui",
         "thisWeek": "Cette semaine",
-        "clear": "Effacer"
+        "clear": "Effacer",
+        "day": "Jour",
+        "weekShort": "Sem."
     },
     "gitea": {
         "settings": {