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/en.json

@@ -351,13 +351,24 @@
   "timeline.day": "Day",
   "timeline.week": "Week",
   "timeline.today": "Today",
-  "timeline.startDate": "Start Date",
+  "timeline.startDate": "Start",
+  "timeline.endDate": "End",
+  "timeline.assignee": "Assignee",
+  "timeline.status": "Status",
   "timeline.dragToMove": "Drag to move",
   "timeline.dragToResize": "Drag edges to resize",
   "timeline.noItems": "No items to display",
   "timeline.addItems": "Add items with dates to see the timeline",
   "timeline.tracks": "Tracks",
   "timeline.timeline": "Timeline",
+  "timeline.item": "Item",
+  "timeline.month": "Month",
+  "timeline.compact": "Compact",
+  "timeline.expand": "Expand",
+  "timeline.resetColor": "Reset to default",
+  "timeline.changeColor": "Change color",
+  "timeline.compactBars": "Compact bars",
+  "timeline.expandedBars": "Expanded bars",
   "posts.details": "Details",
   "posts.platformsLinks": "Platforms & Links",
   "posts.discussion": "Discussion",