fix: Use themeable zap color for active user names

- Replace hardcoded text-orange-400 with text-zap in UserName component
- Replace hardcoded text-orange-400 with text-zap in SpellRenderer ($me placeholder)
- Now uses dark amber/gold with proper contrast on light/plan9 themes

src/components/nostr/UserName.tsx

@@ -13,7 +13,7 @@ interface UserNameProps {
  * Component that displays a user's name from their Nostr profile
  * Shows placeholder derived from pubkey while loading or if no profile exists
  * Clicking opens the user's profile
- * Uses orange-400 color for the logged-in user
+ * Uses zap color for the logged-in user (themeable gold/amber)
  */
 export function UserName({ pubkey, isMention, className }: UserNameProps) {
   const { addWindow, state } = useGrimoire();
@@ -33,7 +33,7 @@ export function UserName({ pubkey, isMention, className }: UserNameProps) {
       dir="auto"
       className={cn(
         "font-semibold cursor-crosshair hover:underline hover:decoration-dotted",
-        isActiveAccount ? "text-orange-400" : "text-accent",
+        isActiveAccount ? "text-zap" : "text-accent",
         className,
       )}
       onClick={handleClick}

src/components/nostr/kinds/SpellRenderer.tsx

@@ -42,7 +42,7 @@ export function MePlaceholder({
   return (
     <span
       className={cn(
-        "inline-flex items-center gap-1.5 font-bold text-orange-400 select-none",
+        "inline-flex items-center gap-1.5 font-bold text-zap select-none",
         pubkey && "cursor-crosshair hover:underline decoration-dotted",
         size === "sm" ? "text-xs" : size === "md" ? "text-sm" : "text-lg",
         className,