docs(qa): before/after evidence for #586

Screenshots at 768px and 820px on the student dashboard and courses list,
plus a scrolled-fully-right frame showing what was unreachable before, and a
pair of GIFs sweeping the viewport from 700px to 1024px.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01183C2p5ed7youHQAUdPfR1

Author: guillermoscript