style(pitch-deck): highlight Professional tier with silver border on BusinessModel slide

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

pitch-deck/components/slides/BusinessModelSlide.tsx

@@ -90,7 +90,7 @@ export default function BusinessModelSlide({ lang, investorId }: BusinessModelSl
           <div className="grid grid-cols-3 gap-3">
             {tiers.map((tier, idx) => (
               <FadeInView key={idx} delay={0.1 + idx * 0.1}>
-                <GlassCard hover={false} className={`p-4 h-full ${tier.highlight ? 'border-indigo-500/40 bg-indigo-500/10 shadow-lg shadow-indigo-500/10' : ''}`}>
+                <GlassCard hover={false} className={`p-4 h-full ${tier.highlight ? 'border-slate-300/40 bg-gradient-to-b from-slate-200/[0.08] to-slate-400/[0.04] shadow-lg shadow-slate-300/10 ring-1 ring-slate-300/20' : ''}`}>
                   <h3 className="text-base font-bold text-white mb-0.5">{tier.name}</h3>
                   <p className="text-xs text-white/40 mb-2">{tier.target}</p>
                   <p className="text-xs text-white/30 mb-3">{tier.employees} {de ? 'Mitarbeiter' : 'employees'}</p>