fix: #3607230 Match the Latest News rail's tabs to the design and use the btn-secondary CTA variant

Issue: https://www.drupal.org/project/vartheme_bs5_horizonaid/issues/3607230

Matches the Latest News rail (impressed-card-slider) filter tabs to the design: they were 16px regular and are now 20px bold (fs-4 fw-bold — this theme's rebuilt Bootstrap scale makes fs-5 16px, fs-4 is the 20px step). The Explore More CTA renders via the standard btn-secondary variant instead of btn-accent; the button atom itself is untouched.

Verified live in a real browser on a Varbase 11 test site: tabs 20px/700, CTA renders through the theme's btn-secondary styling.

Companion recipe MR (light view mode for the card text): horizonaid!40 (merged)

AI-Generated: Yes

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