feat(shared): Länderauswahl mit ISO 3166-1 Mapping und CountryPicker

Backend: Country-Record (Shared Kernel), InMemoryCountryRepository mit
~249 Ländern und DACH-Priorisierung, ListCountries-UseCase,
GET /api/countries?q= Endpoint.

Frontend: CountryPicker-Komponente mit Fuzzy-Suche, DACH-Favoriten bei
leerem Query. SupplierCreate-, CustomerCreate- und AddDeliveryAddress-
Screens verwenden jetzt den CountryPicker statt Freitext. Detail-Screens
zeigen den Ländercode in der Adressanzeige.

Closes #71

frontend/apps/cli/src/components/shared/CountryPicker.tsx

@@ -0,0 +1,129 @@
+import { useState, useMemo } from 'react';
+import { Box, Text, useInput } from 'ink';
+import type { CountryDTO } from '@effigenix/api-client';
+
+interface CountryPickerProps {
+  countries: CountryDTO[];
+  query: string;
+  onQueryChange: (q: string) => void;
+  onSelect: (country: CountryDTO) => void;
+  focus: boolean;
+  selectedName?: string;
+  maxVisible?: number;
+}
+
+const DACH_CODES = ['DE', 'AT', 'CH'];
+
+export function CountryPicker({
+  countries,
+  query,
+  onQueryChange,
+  onSelect,
+  focus,
+  selectedName,
+  maxVisible = 5,
+}: CountryPickerProps) {
+  const [cursor, setCursor] = useState(0);
+
+  const filtered = useMemo(() => {
+    if (!query) {
+      // Show DACH favorites when no query
+      return countries.filter((c) => DACH_CODES.includes(c.code)).slice(0, maxVisible);
+    }
+    const q = query.toLowerCase();
+    return countries.filter(
+      (c) => c.name.toLowerCase().includes(q) || c.code.toLowerCase().includes(q),
+    ).slice(0, maxVisible);
+  }, [countries, query, maxVisible]);
+
+  useInput((input, key) => {
+    if (!focus) return;
+
+    if (key.upArrow) {
+      setCursor((c) => Math.max(0, c - 1));
+      return;
+    }
+    if (key.downArrow) {
+      setCursor((c) => Math.min(filtered.length - 1, c + 1));
+      return;
+    }
+    if (key.return && filtered.length > 0) {
+      const selected = filtered[cursor];
+      if (selected) onSelect(selected);
+      return;
+    }
+    if (key.backspace || key.delete) {
+      onQueryChange(query.slice(0, -1));
+      setCursor(0);
+      return;
+    }
+
+    if (key.tab || key.escape || key.ctrl || key.meta) return;
+
+    if (input && !key.upArrow && !key.downArrow) {
+      onQueryChange(query + input);
+      setCursor(0);
+    }
+  }, { isActive: focus });
+
+  if (!focus && selectedName) {
+    return (
+      <Box flexDirection="column">
+        <Text color="gray">Land *</Text>
+        <Box>
+          <Text color="gray"> › </Text>
+          <Text color="green">✓ {selectedName}</Text>
+        </Box>
+      </Box>
+    );
+  }
+
+  if (focus && selectedName && !query) {
+    return (
+      <Box flexDirection="column">
+        <Text color="cyan">Land * (tippen zum Ändern)</Text>
+        <Box>
+          <Text color="gray"> › </Text>
+          <Text color="green">✓ {selectedName}</Text>
+        </Box>
+        {filtered.length > 0 && (
+          <Box flexDirection="column" paddingLeft={2}>
+            {filtered.map((c, i) => (
+              <Box key={c.code}>
+                <Text color={i === cursor ? 'cyan' : 'white'}>
+                  {i === cursor ? '▶ ' : '  '}{c.code} – {c.name}
+                </Text>
+              </Box>
+            ))}
+          </Box>
+        )}
+      </Box>
+    );
+  }
+
+  return (
+    <Box flexDirection="column">
+      <Text color={focus ? 'cyan' : 'gray'}>Land * (Suche)</Text>
+      <Box>
+        <Text color="gray"> › </Text>
+        <Text>{query || (focus ? '▌' : '')}</Text>
+      </Box>
+      {focus && filtered.length > 0 && (
+        <Box flexDirection="column" paddingLeft={2}>
+          {filtered.map((c, i) => (
+            <Box key={c.code}>
+              <Text color={i === cursor ? 'cyan' : 'white'}>
+                {i === cursor ? '▶ ' : '  '}{c.code} – {c.name}
+              </Text>
+            </Box>
+          ))}
+        </Box>
+      )}
+      {focus && query && filtered.length === 0 && (
+        <Box paddingLeft={2}>
+          <Text color="yellow">Kein Land gefunden.</Text>
+        </Box>
+      )}
+    </Box>
+  );
+}