feat: add separate gradients for Grimoire members based on login state

Updates the UserName component to display different gradient colors for
Grimoire members depending on whether they are the logged-in user:
- Orange-yellow gradient for logged-in Grimoire members (current user)
- Purple-blue gradient for other Grimoire members (not logged in)

This visual distinction makes it easier to identify your own username
versus other Grimoire members in feeds and conversations.

src/components/nostr/UserName.tsx

@@ -15,7 +15,9 @@ interface UserNameProps {
  * Shows placeholder derived from pubkey while loading or if no profile exists
  * Clicking opens the user's profile
  * Uses highlight color for the logged-in user (themeable amber)
- * Shows Grimoire members with yellow-orange gradient styling
+ * Shows Grimoire members with gradient styling:
+ * - Orange-yellow gradient for logged-in Grimoire member
+ * - Purple-blue gradient for other Grimoire members
  */
 export function UserName({ pubkey, isMention, className }: UserNameProps) {
   const { addWindow, state } = useGrimoire();
@@ -37,7 +39,9 @@ export function UserName({ pubkey, isMention, className }: UserNameProps) {
       className={cn(
         "font-semibold cursor-crosshair hover:underline hover:decoration-dotted",
         isGrimoire
-          ? "bg-gradient-to-br from-yellow-500 via-orange-500 to-orange-600 bg-clip-text text-transparent"
+          ? 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-cyan-500 bg-clip-text text-transparent"
           : isActiveAccount
             ? "text-highlight"
             : "text-accent",