feat(01-03): create PeopleList component

- Subscribes to store.people signal
- Renders list of person names with unique keys
- Shows empty state when no people added
- Preact Signals auto-track dependencies in components

gsd-framework/src/components/people/PeopleList.jsx

@@ -0,0 +1,17 @@
+import { store } from '../../store/billStore.js';
+
+export function PeopleList() {
+  const people = store.people.value;
+
+  if (people.length === 0) {
+    return <p class="empty-state">No people added yet</p>;
+  }
+
+  return (
+    <ul class="people-list">
+      {people.map((person) => (
+        <li key={person.id}>{person.name}</li>
+      ))}
+    </ul>
+  );
+}