Normalize + Adapt: CSS tokens, RTL fixes, mobile nav, fluid charts

Normalize:
- Add 10+ new CSS variables (brand-icon, brand-text, text-inverse, warning-*, etc.)
- Replace 35+ hardcoded hex colors with CSS variable references

Adapt:
- Add Slides link to mobile bottom nav (was unreachable on mobile)
- Fix RTL table alignment: text-align left → start
- Make chart height fluid: 380px → clamp(280px, 30vw, 420px)
- Fix carousel dot touch targets to minimum 24px
- Fix margin-left → margin-inline-start for RTL

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/App.tsx

@@ -224,6 +224,14 @@ function App() {
             </svg>
             <span>{t('nav.compare')}</span>
           </NavLink>
+          <NavLink to="/slides" className="mobile-nav-item">
+            <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
+              <rect x="2" y="3" width="20" height="14" rx="2"/>
+              <line x1="8" y1="21" x2="16" y2="21"/>
+              <line x1="12" y1="17" x2="12" y2="21"/>
+            </svg>
+            <span>{t('nav.slides')}</span>
+          </NavLink>
           <button
             className="mobile-nav-item"
             onClick={switchLanguage}