fix: show placeholder badge for defunct nations with no flag-icons code

Soviet Union (su), Yugoslavia (yu), East Germany, Germany DR, FR Yugoslavia,
and Czechoslovakia have no valid entry in flag-icons. Map them to null in
TEAM_ISO so getIso() returns null, and render a muted initials badge in
TeamFlag instead of a broken/empty sprite. Also drop the buggy 2-char
substring fallback that generated random valid codes for unknown teams.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/team-flag.tsx

@@ -9,8 +9,42 @@ interface Props {
 
 const sizes = { sm: 'text-lg', md: 'text-2xl', lg: 'text-4xl', xl: 'text-[60px]' }
 
+const placeholderSize = {
+  sm:  { width: '1.35em', height: '1em',    fontSize: '0.38em' },
+  md:  { width: '1.35em', height: '1em',    fontSize: '0.38em' },
+  lg:  { width: '1.35em', height: '1em',    fontSize: '0.38em' },
+  xl:  { width: '1.35em', height: '1em',    fontSize: '0.38em' },
+}
+
 export function TeamFlag({ name, iso2, size = 'md', className = '' }: Props) {
-  const code = iso2 ?? getIso(name)
+  const code = iso2 !== undefined ? iso2 : getIso(name)
+
+  if (!code) {
+    const abbr = name
+      .split(/\s+/)
+      .map(w => w[0])
+      .join('')
+      .slice(0, 3)
+      .toUpperCase()
+    return (
+      <span
+        className={`rounded-sm inline-flex items-center justify-center flex-shrink-0 ${sizes[size]} ${className}`}
+        style={{
+          ...placeholderSize[size],
+          background: 'rgba(42,92,53,0.35)',
+          color: '#6abf7a',
+          fontFamily: 'Space Grotesk, sans-serif',
+          fontWeight: 700,
+          letterSpacing: '0.04em',
+          lineHeight: 1,
+        }}
+        title={name}
+      >
+        {abbr}
+      </span>
+    )
+  }
+
   return (
     <span
       className={`fi fi-${code} rounded-sm inline-block flex-shrink-0 ${sizes[size]} ${className}`}