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/components/ArtefactVersionTimeline.jsx

@@ -19,7 +19,7 @@ export default function ArtefactVersionTimeline({ versions, activeVersionId, onS
           <button
             key={version.Id}
             onClick={() => onSelectVersion(version)}
-            className={`w-full text-left p-3 rounded-lg border transition-colors ${
+            className={`w-full text-start p-3 rounded-lg border transition-colors ${
               isActive
                 ? 'border-brand-primary bg-brand-primary/5'
                 : 'border-border hover:border-brand-primary/30 bg-surface hover:shadow-sm'
@@ -80,7 +80,7 @@ export default function ArtefactVersionTimeline({ versions, activeVersionId, onS
 
             {/* Thumbnail for image artefacts */}
             {artefactType === 'design' && version.thumbnail && (
-              <div className="mt-2 ml-11">
+              <div className="mt-2 ms-11">
                 <img
                   src={version.thumbnail}
                   alt={`Version ${version.version_number}`}