refine: reposition blue to match yellow placement in gradients

Rearranges the purple-blue gradient to start with blue-400 (matching
the top-left position of yellow-500 in the orange-yellow gradient) and
transition through purple-500 to purple-600.

Gradient order:
- Logged-in: yellow → orange → orange
- Other members: blue → purple → purple

src/components/nostr/UserName.tsx

@@ -41,7 +41,7 @@ export function UserName({ pubkey, isMention, className }: UserNameProps) {
         isGrimoire
           ? isActiveAccount
             ? "bg-gradient-to-br from-yellow-500 via-orange-500 to-orange-600 bg-clip-text text-transparent"
-            : "bg-gradient-to-br from-purple-500 via-purple-600 to-blue-400 bg-clip-text text-transparent"
+            : "bg-gradient-to-br from-blue-400 via-purple-500 to-purple-600 bg-clip-text text-transparent"
           : isActiveAccount
             ? "text-highlight"
             : "text-accent",