feat: alphabet list, change Layout etc

lib/utils/name_index.dart

@@ -0,0 +1,35 @@
+/// Letters of an A–Z index; names that don't start with a letter go under `#`.
+final indexLetters = [...'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split(''), '#'];
+
+const _accented = 'ÀÁÂÃÄÅÇÈÉÊËÌÍÎÏÑÒÓÔÕÖÙÚÛÜÝŸ';
+const _unaccented = 'AAAAAACEEEEIIIINOOOOOUUUUYY';
+
+/// Uppercase without accents, so "Émile" sorts and indexes under E.
+String _fold(String name) {
+  return [
+    for (final char in name.trim().toUpperCase().split(''))
+      switch (_accented.indexOf(char)) {
+        -1 => char,
+        final index => _unaccented[index],
+      },
+  ].join();
+}
+
+String indexLetterOf(String name) {
+  final folded = _fold(name);
+  if (folded.isEmpty) return '#';
+
+  final first = folded[0];
+  return indexLetters.contains(first) ? first : '#';
+}
+
+/// A–Z regardless of case and accents, with the `#` names last.
+int compareByIndex(String a, String b) {
+  final byLetter = indexLetters
+      .indexOf(indexLetterOf(a))
+      .compareTo(indexLetters.indexOf(indexLetterOf(b)));
+  if (byLetter != 0) return byLetter;
+
+  final byName = _fold(a).compareTo(_fold(b));
+  return byName != 0 ? byName : a.compareTo(b);
+}