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/app/dashboard/ai-coach/tutor/page.tsx

@@ -1,4 +1,4 @@
-"use client"
+"use client"
 
 import { TutorChat } from "@/components/AI/TutorChat"
 import { BrainCircuit, Sparkles, MessageSquare, Lightbulb } from "lucide-react"
@@ -6,7 +6,7 @@ import { Card, CardContent } from "@/components/ui/card"
 
 const CAPABILITIES = [
   { icon: <Lightbulb size={16} className="text-yellow-400" />, label: "Concept Explanations", desc: "Step-by-step breakdown of Physics, Chemistry, Maths & Biology topics" },
-  { icon: <Sparkles size={16} className="text-[#00F0FF]" />, label: "Problem Solving", desc: "Full worked solutions with formulas, derivations and shortcuts" },
+  { icon: <Sparkles size={16} className="text-[var(--cyan-ai)]" />, label: "Problem Solving", desc: "Full worked solutions with formulas, derivations and shortcuts" },
   { icon: <MessageSquare size={16} className="text-green-400" />, label: "Doubt Clearing", desc: "Ask follow-up questions — the AI remembers context within the session" },
 ]
 
@@ -18,8 +18,8 @@ export default function TutorChatPage() {
         <div className="flex items-start justify-between gap-4 flex-wrap">
           <div>
             <h1 className="text-3xl md:text-4xl font-black tracking-tight flex items-center gap-3 mb-2">
-              <span className="p-2.5 rounded-xl bg-cyan-50 dark:bg-[#00F0FF]/10 border border-cyan-300/60 dark:border-[#00F0FF]/20">
-                <BrainCircuit className="text-cyan-700 dark:text-[#00F0FF]" size={28} />
+              <span className="p-2.5 rounded-xl bg-cyan-50 dark:bg-[var(--cyan-ai-10)] border border-cyan-300/60 dark:border-[var(--cyan-ai-20)]">
+                <BrainCircuit className="text-cyan-700 dark:text-[var(--cyan-ai)]" size={28} />
               </span>
               AI Tutor — 24/7 Doubt Solver
             </h1>