fix(BUY-64263): clarify homepage CTA hierarchy

[BuyWhere]

Summary

• keep Browse price comparisons as the solid white primary CTA
• restyle Developers: Get API access as a transparent white-outline secondary CTA
• preserve white text and add a subtle white hover fill

Verification

• observed the running homepage at 1440px: primary computed background rgb(255,255,255); secondary transparent with rgba(255,255,255,0.4) border
• observed both CTAs visible and full-width at 375px with no horizontal overflow
• no failed browser requests during the desktop probe

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