The CSP was missing a default-src directive (flagged by CodeRabbit).
Without it, styles, images, fonts, and media are completely
unrestricted, which undercuts the otherwise strict policy.
Set default-src to 'self' and add an explicit style-src directive
since we rely on inline styles (e.g. #close-msg and the view
toggling use inline style attributes), so style-src needs to allow
'self' and 'unsafe-inline'.