refactor: create reusable ExternalLink component for consistent styling

Create ExternalLink component following patterns from HighlightRenderer and
BookmarkRenderer with:
- Two variants: 'muted' (default, text-muted-foreground with underline)
  and 'default' (text-primary with hover:underline)
- Three sizes: xs, sm, base
- Configurable icon display
- Consistent truncate behavior for long URLs
- Stop propagation on click

Apply to NIP-89 renderers:
- ApplicationHandlerRenderer: uses muted variant (feed view)
- ApplicationHandlerDetailRenderer: uses default variant (detail view)

This ensures consistent link styling across the entire application
and makes it easy to maintain a unified design language.

src/components/ExternalLink.tsx

@@ -0,0 +1,65 @@
+import { ExternalLink as ExternalLinkIcon } from "lucide-react";
+import { cn } from "@/lib/utils";
+
+interface ExternalLinkProps {
+  href: string;
+  children: React.ReactNode;
+  className?: string;
+  iconClassName?: string;
+  showIcon?: boolean;
+  variant?: "default" | "muted";
+  size?: "xs" | "sm" | "base";
+}
+
+/**
+ * Reusable external link component with consistent styling across the app
+ * Follows patterns from HighlightRenderer and BookmarkRenderer
+ */
+export function ExternalLink({
+  href,
+  children,
+  className,
+  iconClassName,
+  showIcon = true,
+  variant = "muted",
+  size = "xs",
+}: ExternalLinkProps) {
+  const sizeClasses = {
+    xs: "text-xs",
+    sm: "text-sm",
+    base: "text-base",
+  };
+
+  const iconSizeClasses = {
+    xs: "size-3",
+    sm: "size-3",
+    base: "size-4",
+  };
+
+  const variantClasses = {
+    default: "text-primary hover:underline",
+    muted: "text-muted-foreground underline decoration-dotted",
+  };
+
+  return (
+    <a
+      href={href}
+      target="_blank"
+      rel="noopener noreferrer"
+      className={cn(
+        "inline-flex items-center gap-1",
+        sizeClasses[size],
+        variantClasses[variant],
+        className,
+      )}
+      onClick={(e) => e.stopPropagation()}
+    >
+      {showIcon && (
+        <ExternalLinkIcon
+          className={cn("flex-shrink-0", iconSizeClasses[size], iconClassName)}
+        />
+      )}
+      <span className="truncate">{children}</span>
+    </a>
+  );
+}

src/components/nostr/kinds/ApplicationHandlerDetailRenderer.tsx

@@ -11,13 +11,13 @@ import { KindBadge } from "@/components/KindBadge";
 import { Badge } from "@/components/ui/badge";
 import { useCopy } from "@/hooks/useCopy";
 import { UserName } from "../UserName";
+import { ExternalLink } from "@/components/ExternalLink";
 import {
   Copy,
   CopyCheck,
   Globe,
   Smartphone,
   TabletSmartphone,
-  ExternalLink,
 } from "lucide-react";
 
 interface ApplicationHandlerDetailRendererProps {
@@ -94,15 +94,9 @@ export function ApplicationHandlerDetailRenderer({
 
         {/* Website */}
         {website && (
-          <a
-            href={website}
-            target="_blank"
-            rel="noopener noreferrer"
-            className="inline-flex items-center gap-1 text-primary hover:underline"
-          >
+          <ExternalLink href={website} variant="default" size="base">
             {website}
-            <ExternalLink className="size-3" />
-          </a>
+          </ExternalLink>
         )}
 
         {/* Metadata Grid */}

src/components/nostr/kinds/ApplicationHandlerRenderer.tsx

@@ -11,6 +11,7 @@ import {
 } from "@/lib/nip89-helpers";
 import { KindBadge } from "@/components/KindBadge";
 import { Badge } from "@/components/ui/badge";
+import { ExternalLink } from "@/components/ExternalLink";
 import { Globe, Smartphone, TabletSmartphone } from "lucide-react";
 
 /**
@@ -60,17 +61,7 @@ export function ApplicationHandlerRenderer({ event }: BaseEventProps) {
         </ClickableEventTitle>
 
         {/* Website */}
-        {website && (
-          <a
-            href={website}
-            target="_blank"
-            rel="noopener noreferrer"
-            className="text-xs text-primary hover:underline"
-            onClick={(e) => e.stopPropagation()}
-          >
-            {website}
-          </a>
-        )}
+        {website && <ExternalLink href={website}>{website}</ExternalLink>}
 
         {/* Supported Kinds */}
         {displayKinds.length > 0 && (