fix: RTL support for timelines and header dropdown

- InteractiveTimeline: dir="ltr" on scroll area, i18n for all strings
- ArtefactVersionTimeline: text-start, ms-11 logical properties
- Header dropdown: end-0 instead of right-0, text-start on menu items
- Added 11 new timeline i18n keys (en + ar)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/i18n/ar.json

@@ -351,13 +351,24 @@
   "timeline.day": "يوم",
   "timeline.week": "أسبوع",
   "timeline.today": "اليوم",
-  "timeline.startDate": "تاريخ البدء",
+  "timeline.startDate": "البداية",
+  "timeline.endDate": "النهاية",
+  "timeline.assignee": "المُكلّف",
+  "timeline.status": "الحالة",
   "timeline.dragToMove": "اسحب للنقل",
   "timeline.dragToResize": "اسحب الحواف لتغيير الحجم",
   "timeline.noItems": "لا توجد عناصر للعرض",
   "timeline.addItems": "أضف عناصر بتواريخ لعرض الجدول الزمني",
   "timeline.tracks": "المسارات",
   "timeline.timeline": "الجدول الزمني",
+  "timeline.item": "العنصر",
+  "timeline.month": "شهر",
+  "timeline.compact": "مضغوط",
+  "timeline.expand": "موسّع",
+  "timeline.resetColor": "إعادة إلى الافتراضي",
+  "timeline.changeColor": "تغيير اللون",
+  "timeline.compactBars": "أشرطة مضغوطة",
+  "timeline.expandedBars": "أشرطة موسّعة",
   "posts.details": "التفاصيل",
   "posts.platformsLinks": "المنصات والروابط",
   "posts.discussion": "النقاش",