fix: use solid colors for BadgeCheck icon (gradients don't work on SVG)

The bg-clip-text technique only works on actual text elements, not SVG
paths. Reverted to solid colors that complement the gradient themes:

- Logged-in: text-amber-500 (matches the amber gradient tones)
- Others: text-fuchsia-500 (matches the fuchsia gradient tones)

The icon is now visible and color-coordinated with the username gradients.

src/components/nostr/UserName.tsx

@@ -62,9 +62,7 @@ export function UserName({ pubkey, isMention, className }: UserNameProps) {
         <BadgeCheck
           className={cn(
             "inline-block w-[1em] h-[1em]",
-            isActiveAccount
-              ? "bg-gradient-to-tr from-amber-600 to-amber-400 bg-clip-text text-transparent"
-              : "bg-gradient-to-tr from-fuchsia-600 to-fuchsia-400 bg-clip-text text-transparent",
+            isActiveAccount ? "text-amber-500" : "text-fuchsia-500",
           )}
         />
       )}