refactor(decnet_web/AttackerDetail): extract AttackerHeader section

Lift the header (IP, country tag, traversal badge, identity badge)
into its own section component. Tag helper moves to a shared
AttackerDetail/ui.tsx so future sections can reuse it without
re-importing through AttackerDetail.tsx.

- New AttackerDetail/sections/AttackerHeader.tsx (~50 LOC)
- New AttackerDetail/ui.tsx for shared presentational helpers
- AttackerDetail.tsx imports both; local Tag definition deleted
- AttackerHeader.test.tsx covers country present/absent,
  TRAVERSAL badge, IDENTITY click-through, identity null path

decnet_web/src/components/AttackerDetail/ui.tsx

@@ -0,0 +1,22 @@
+import React from 'react';
+
+/** Pill-style tag chip used throughout the AttackerDetail surface
+ *  for badges, filters, and category labels. Color drives both the
+ *  border and a 15%-alpha fill (the suffix is hex alpha). */
+export const Tag: React.FC<{ children: React.ReactNode; color?: string }> = ({
+  children,
+  color,
+}) => (
+  <span
+    style={{
+      fontSize: '0.7rem',
+      padding: '2px 8px',
+      letterSpacing: '1px',
+      border: `1px solid ${color || 'var(--text-color)'}`,
+      color: color || 'var(--text-color)',
+      background: `${color || 'var(--text-color)'}15`,
+    }}
+  >
+    {children}
+  </span>
+);