Add stage 4: frontend lists view + enforce 100-list cap

API: GET /api/lists is now ordered alphabetically (COLLATE NOCASE) by title
with no other option, and TodoListController rejects a create past 100 lists
per owner with 409. New TodoListRepository::countForOwner.

Frontend: HomeView replaces the placeholder with the user's lists (rendered in
API order) and a create form (title + optional description). New Pinia lists
store fetches and creates, re-fetching after a create so the new list sorts
into place; it is reset on logout. Form disables and explains at 100 lists;
create errors surface inline. Neutral .badge with a .badge--warn variant;
dropped the unused .facts styles.

Tests: alphabetical ordering and the 100-list cap. Suite: 17 passing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/stores/lists.ts

@@ -0,0 +1,44 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { apiRequest } from '../lib/api'
+import type { TodoList } from '../types'
+
+/** Matches MAX_LISTS_PER_OWNER on the API. */
+export const MAX_LISTS = 100
+
+export const useListsStore = defineStore('lists', () => {
+  // Kept in the order the API returns them (alphabetical by title).
+  const lists = ref<TodoList[]>([])
+  const loaded = ref(false)
+  const loading = ref(false)
+
+  async function fetchLists(): Promise<void> {
+    loading.value = true
+    try {
+      const { lists: fetched } = await apiRequest<{ lists: TodoList[] }>('/lists', { auth: true })
+      lists.value = fetched
+      loaded.value = true
+    } finally {
+      loading.value = false
+    }
+  }
+
+  async function createList(title: string, description: string): Promise<TodoList> {
+    const { list } = await apiRequest<{ list: TodoList }>('/lists', {
+      method: 'POST',
+      auth: true,
+      body: { title, description },
+    })
+
+    // Re-fetch so the new list lands in its correct alphabetical position.
+    await fetchLists()
+    return list
+  }
+
+  function reset(): void {
+    lists.value = []
+    loaded.value = false
+  }
+
+  return { lists, loaded, loading, fetchLists, createList, reset }
+})