feat: add coming soon section and device notice to landing page

- Add "Coming Soon" section with Cloud Sync, Achievements, JavaScript, Frameworks
- Add device notice recommending desktop/tablet for best experience
- Add translations for all 6 languages (en, de, pl, es, ar, uk)
- Add CSS styling with responsive grid layout

🤖 Generated with [Claude Code](https://claude.com/claude-code)

src/index.html

@@ -169,6 +169,38 @@
 						</div>
 					</section>
 
+					<section class="coming-soon">
+						<h2 data-i18n="landingComingSoonTitle">Coming Soon</h2>
+						<div class="coming-soon-grid">
+							<article class="coming-soon-card">
+								<span class="coming-soon-icon">🔄</span>
+								<h3 data-i18n="comingSoonSyncTitle">Cloud Sync</h3>
+								<p data-i18n="comingSoonSyncText">Sync your progress across all devices. Start on desktop, continue on tablet.</p>
+							</article>
+							<article class="coming-soon-card">
+								<span class="coming-soon-icon">🏆</span>
+								<h3 data-i18n="comingSoonAchievementsTitle">Achievements</h3>
+								<p data-i18n="comingSoonAchievementsText">Earn badges as you master new skills. Track your learning milestones.</p>
+							</article>
+							<article class="coming-soon-card">
+								<span class="coming-soon-icon">⚡</span>
+								<h3 data-i18n="comingSoonJsTitle">JavaScript</h3>
+								<p data-i18n="comingSoonJsText">Interactive JavaScript lessons with live code execution and DOM manipulation.</p>
+							</article>
+							<article class="coming-soon-card">
+								<span class="coming-soon-icon">🧩</span>
+								<h3 data-i18n="comingSoonFrameworksTitle">Frameworks</h3>
+								<p data-i18n="comingSoonFrameworksText">React, Vue, and Svelte basics. Build real components step by step.</p>
+							</article>
+						</div>
+					</section>
+
+					<section class="device-notice">
+						<p data-i18n="deviceNotice">
+							<strong>Best on desktop or tablet (landscape).</strong> Mobile works, but larger screens make coding easier.
+						</p>
+					</section>
+
 					<section class="landing-cta">
 						<h2 data-i18n="landingCtaTitle">Start Learning Today</h2>
 						<a href="#welcome/0" class="cta-button" data-i18n="landingCtaButton">Begin Your Journey</a>