msglist: Use directional positioning for unread marker in RTL

[yash-agarwa-l]

Fixes #1245

This PR corrects the unread-marker alignment in RTL layouts.

Problem:
_UnreadMarker used LTR-specific properties (left: 0, Border(left: …)), causing the unread marker to always appear on the left, even for RTL languages like Arabic.

Fix
Therefore Replaced LTR-specific properties with directional equivalents:
PositionedDirectional(start: 0)
BorderDirectional(start: BorderSide(...))

This ensures the unread marker appears on the correct “start” side based on text direction.

Manually tested by setting:
locale: Locale('ar')

Verified correct behavior in both LTR and RTL layouts (screenshots included).

Before

LTR

RTL

After

LTR

RTL

[chrisbobbe]

Thanks! Small comments below.

Also:

• Please say Fixes #1245. in the commit message. For examples, use Greg's "secret" to using git log -p.
• Please also post screenshots of what it looks like before this change, so we can see clearly the improvement being made. 🙂

[chrisbobbe]

Same here.

[chrisbobbe]

This code-style change is unrelated and unhelpful; please remove it.

[yash-agarwa-l]

Thank you for the feedback.
I’ve cleaned up the commit and added the before screenshots as requested.
Please let me know if there’s anything else I should adjust.

[chrisbobbe]

Bump on this part:

• Please say Fixes #1245. in the commit message. For examples, use Greg's "secret" to using git log -p.

[yash-agarwa-l]

Thank You, I've updated the commit and pushed the revision.

[chrisbobbe]

Please write it according to the project style; the Fixes #1245. line belongs in the commit-message body, not in the summary line.

[yash-agarwa-l]

Thanks for the clarification, updated.

[chrisbobbe]

Thanks! Marked for Greg's review.