Properties: swap 'Key custody / No one holds them' for pricing

Replace the vague custody stat with the concrete billing model:
'Pricing / $0.01 per second'. The adjacent 'Latency / Sub-second
signing' stat lets readers do the per-signature math without
spelling it out, and $/sec is the actual meter so it holds up
when an action runs longer.

Author: glitch003

src/components/LandingHowItWorks/LandingHowItWorks.tsx

@@ -136,7 +136,7 @@ const LandingHowItWorks = () => {
             <div className="grid grid-cols-2 gap-4">
               <Stat k="Latency" v="Sub-second signing" />
               <Stat k="Auditability" v="Code hash on-chain" />
-              <Stat k="Key custody" v="No one holds them" />
+              <Stat k="Pricing" v="$0.01 per second" />
               <Stat k="Surface" v="Any HTTP, any chain" />
             </div>
           </div>

src/components/Prototypes/Prototype1.tsx

@@ -162,7 +162,7 @@ export default function Prototype1() {
             <div className="grid grid-cols-2 gap-4">
               <Stat k="Latency" v="Sub-second signing" />
               <Stat k="Auditability" v="Code hash on-chain" />
-              <Stat k="Key custody" v="No one holds them" />
+              <Stat k="Pricing" v="$0.01 per second" />
               <Stat k="Surface" v="Any HTTP, any chain" />
             </div>
           </div>