Hallmark Cobalt: unified light palette + Ubuntu fonts

Layout: Ubuntu + Ubuntu Mono (next/font/google), light mode
CSS: Hallmark Cobalt palette — cool paper bg, hairlines,
  electric cobalt primary, slate secondary
Cards: white bg, hairline borders, muted type badges
Header/tabs: Ubuntu Mono labels, Ubuntu tab buttons
Removed: dark mode, Inter/JetBrains Mono, purple gradients

dashboard-next/src/app/page.tsx

@@ -307,14 +307,14 @@ export default function Dashboard() {
       <header className="sticky top-0 z-50 border-b border-[#e0e4ec] bg-[#f8f9fb]/95 backdrop-blur-sm">
         <div className="flex items-center justify-between px-6 h-12 max-w-[1440px] mx-auto">
           <div className="flex items-center gap-5">
-            <span className="text-[11px] font-medium tracking-[0.04em] text-[#1a1c23]" style={{fontFamily:"JetBrains Mono, monospace"}}>
+            <span className="text-[11px] font-medium tracking-[0.04em] text-[#1a1c23]" style={{fontFamily:"'Ubuntu Mono', monospace"}}>
               {tab === "live" ? "Live Testnet" : tab === "paper" ? "Paper Mainnet" : "Historical"}
             </span>
           </div>
           <div className="flex items-center gap-4">
             <span className="flex items-center gap-1.5">
               <span className={`w-1.5 h-1.5 rounded-full ${liveConn ? "bg-[#0ea5e9]" : "bg-[#e5e7eb]"}`} />
-              <span className="text-[9px] text-[#6e7381] font-medium tracking-[0.03em]" style={{fontFamily:"JetBrains Mono, monospace"}}>
+              <span className="text-[9px] text-[#6e7381] font-medium tracking-[0.03em]" style={{fontFamily:"'Ubuntu Mono', monospace"}}>
                 {liveConn ? "CONNECTED" : "OFFLINE"} · {liveData?.status ?? "···"}
               </span>
             </span>
@@ -329,7 +329,7 @@ export default function Dashboard() {
             <button
               key={t}
               onClick={() => setTab(t)}
-              style={{fontFamily:"Inter, sans-serif"}}
+              style={{fontFamily:"'Ubuntu', sans-serif"}}
               className={`relative px-4 py-2.5 text-xs font-medium tracking-[0.02em] transition-colors cursor-pointer
                 ${tab === t
                   ? "text-[#1a1c23] after:absolute after:bottom-0 after:left-0 after:right-0 after:h-[2px] after:bg-[#0ea5e9]"