feat(04-01): wire BrowserRouter + BottomTabBar + empty Lists surface

- App.tsx: BrowserRouter with /calendar, /lists, /lists/:listId routes; / redirects to /calendar
- BottomTabBar.tsx: fixed-bottom 56px tab bar with Calendar + Lists NavLinks, active accent
- AppNav.tsx: add Calendar/Lists NavLinks to desktop sidebar (≥768px)
- ListsIndex.tsx: full-height surface with isLoading/isError/empty state branches; "+ New List" FAB placeholder
- ListDetail.tsx: placeholder stub for /lists/:listId (Plan 04-04 fills in)
- listsStore.ts: Zustand UI-only store (activeTab, createListSheetOpen)
- listsClient.ts: fetchLists + List/ListItem types (initial; Plans 04-02/03 expand)
- Fix Wave-0 RED stubs: add vitest imports so stubs execute (todo) not error on import
- Fix CalendarShell.test.tsx: wrap renderWithClient in MemoryRouter (AppNav uses NavLink)

apps/pwa/src/api/listsClient.ts

@@ -0,0 +1,47 @@
+/**
+ * Typed API client for the FamilySync lists API.
+ *
+ * credentials: 'include' is required so the OIDC session cookie is sent with
+ * every request (same pattern as client.ts).
+ *
+ * This file provides only the functions needed in Plan 04-01 (ListsIndex empty
+ * state). Plans 04-02 and 04-03 expand it with createList, deleteList, item CRUD.
+ */
+
+const BASE = '/api'
+
+async function apiFetch(path: string, init?: RequestInit): Promise<Response> {
+  const res = await fetch(`${BASE}${path}`, {
+    credentials: 'include',
+    ...init,
+  })
+  if (!res.ok) throw new Error(`${init?.method ?? 'GET'} ${path} failed: ${res.status}`)
+  return res
+}
+
+// ── Types ──────────────────────────────────────────────────────────────────
+
+export interface List {
+  id: number
+  name: string
+  isShared: boolean
+  ownerId: number
+}
+
+export interface ListItem {
+  id: number
+  listId: number
+  text: string
+  checked: boolean
+  rank: string
+}
+
+export interface ListsResponse {
+  lists: List[]
+}
+
+// ── Functions ──────────────────────────────────────────────────────────────
+
+export async function fetchLists(): Promise<ListsResponse> {
+  return apiFetch('/lists').then((r) => r.json() as Promise<ListsResponse>)
+}