Demo and small UI fixes

[mosin74]

Overview

1. This PR fixes or fixes part of #[fill_in_number_here].
2. This PR does the following:

• Score percentages should be whole numbers:

• Update certificate icon in the Learner Dashboard

• Use more neutral colors in the failure screen

• Take screenshots with different languages/Learner Experience should flip for RTL languages

- Continue to assessment button needs more padding

• Learner experience needs to be mobile-ready

Screencast.from.2026-09-06.06-48-19.webm

Essential Checklist

Please follow the instructions for making a code change.

• I have linked the issue that this PR fixes in the "Development" section of the sidebar.
• I have checked the "Files Changed" tab and confirmed that the changes are what I want to make.
• I have written tests for my code.
• The PR title starts with "Fix #bugnum: " or "Fix part of #bugnum: ...", followed by a short, clear summary of the changes.
• I have assigned the correct reviewers to this PR (or will leave a comment with the phrase "@{{reviewer_username}} PTAL" if I can't assign them directly).

Proof that changes are correct

Proof of changes on desktop with slow/throttled network

Proof of changes on mobile phone

Proof of changes in Arabic language

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