design: cyan -> rgb(12,96,96) in light theme, #00F0FF stays in dark theme

- globals.css: add --cyan-ai CSS variable (rgb(12,96,96) light / #00F0FF dark)
  + opacity variants --cyan-ai-10/20/30/40/50/80
- Bulk replace all #00F0FF hardcoded Tailwind arbitrary values with
  var(--cyan-ai) / var(--cyan-ai-10) / etc across 55+ TSX/TS files
- Shadow glow colours also updated (suppressed by box-shadow:none in light mode)
- TypeScript: 0 errors

src/components/TierBadge.tsx

@@ -1,4 +1,4 @@
-import { Badge } from "@/components/ui/badge"
+import { Badge } from "@/components/ui/badge"
 
 interface TierBadgeProps {
   tier: "Free" | "Pro" | "AI Coach"
@@ -14,7 +14,7 @@ export function TierBadge({ tier }: TierBadgeProps) {
   }
   
   return (
-    <Badge className="text-xs font-semibold uppercase tracking-wider bg-cyan-500/10 text-cyan-700 dark:text-cyan-400 border-cyan-500/20 hover:bg-cyan-500/20 transition-colors shadow-none dark:shadow-[0_0_10px_-2px_#00F0FF]">
+    <Badge className="text-xs font-semibold uppercase tracking-wider bg-cyan-500/10 text-cyan-700 dark:text-cyan-400 border-cyan-500/20 hover:bg-cyan-500/20 transition-colors shadow-none dark:shadow-[0_0_10px_-2px_var(--cyan-ai)]">
       AI Coach
     </Badge>
   )