fix: resolve coloring book section layout on small viewports

[Rickydama3]

Concisely describe the change

This PR fixes a responsive layout bug where the Coloring Book section would break and disappear on viewports smaller than lg.

The issue was caused by conflicting Tailwind utility classes:

• The cover image had a hidden lg:block class causing it to vanish completely on small screens.
• The flex layout lacked the base flex class.
• The flex ordering pushed the collage above the text on small screens.

This update removes the hidden attribute, applies the correct base flex class, adjusts the order logic for a clean vertical stack on mobile, and adds proper margins to prevent overlapping.

Fixes #557

N/A - See Issue #557 for original bug recording.

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