(SP: 2) [Frontend] Improve Lighthouse Performance and SEO scores for quiz pages

[LesiaUKR]

Goal

Improve Lighthouse Performance (85->90+) and SEO (82->100) scores for quiz pages.

Scope

• Remove unused Font Awesome CSS import (render-blocking, ~780ms)
• Add .browserslistrc to target modern browsers (reduce polyfills ~14 KiB)
• Add generateMetadata() for /quizzes and /quiz/[slug] pages with i18n
• Add meta translations to en.json, uk.json, pl.json
• Replace emoji with lucide-react <Clock /> icon in CountdownTimer

Expected impact

Metric	Before	After
Render blocking CSS	~780ms	0ms
Legacy JS polyfills	~14 KiB	~0 KiB
SEO score	82	100
Performance score	85	90+

Out of scope

• LCP optimization via server components refactoring
• Lato font removal (used in BlogHeaderSearch)