docs(meeting): restyle 30th meeting pages (ko/en)

[soimkim]

Summary

• Redesign the 30th meeting pages in both Korean and English with a conference-style layout
• Apply a KakaoBank-inspired yellow visual theme to hero, highlight cards, agenda timeline cards, and sponsor section
• Keep existing meeting content while improving readability and presentation structure

Test plan

• Run local Hugo build (npm run _hugo-dev -- --minify)
• Verify KO page renders at /meeting/2026/30th/
• Verify EN page renders at /en/meeting/2026/30th/

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