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/routes/ListDetail.tsx

@@ -0,0 +1,46 @@
+/**
+ * ListDetail — Single list view (/lists/:listId).
+ *
+ * PLACEHOLDER: This is a stub route component for Plan 04-01.
+ * The full implementation (items, SSE, drag-to-reorder, etc.) is built in Plan 04-04.
+ *
+ * Purpose: allows react-router's /lists/:listId route to resolve without error
+ * so the BottomTabBar NavLink and any deep-link won't 404.
+ */
+
+export function ListDetail() {
+  return (
+    <div
+      style={{
+        display: 'flex',
+        flexDirection: 'column',
+        alignItems: 'center',
+        justifyContent: 'center',
+        height: '100%',
+        gap: '12px',
+        fontFamily: 'var(--font-family-base)',
+        padding: '0 var(--space-4, 16px)',
+        textAlign: 'center',
+        paddingBottom: 'calc(56px + env(safe-area-inset-bottom, 0px))',
+      }}
+    >
+      <div
+        style={{
+          fontSize: 'var(--text-heading-size, 18px)',
+          fontWeight: 600,
+          color: 'var(--color-text-primary)',
+        }}
+      >
+        List view coming soon
+      </div>
+      <div
+        style={{
+          fontSize: 'var(--text-body-size, 15px)',
+          color: 'var(--color-text-muted)',
+        }}
+      >
+        Full list detail with live sync is being built in Phase 4 Plan 4.
+      </div>
+    </div>
+  )
+}