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>

src/Repository/TodoListRepository.php

@@ -28,16 +28,29 @@ final class TodoListRepository
     }
 
     /**
+     * Every list owned by the user, always sorted alphabetically by title
+     * (case-insensitive). There is deliberately no other ordering option.
+     *
      * @return TodoListRow[]
      */
     public function allForOwner(int $ownerId): array
     {
-        $stmt = $this->pdo->prepare(self::SELECT . ' WHERE l.owner_id = :owner ORDER BY l.created_at DESC, l.id DESC');
+        $stmt = $this->pdo->prepare(
+            self::SELECT . ' WHERE l.owner_id = :owner ORDER BY l.title COLLATE NOCASE ASC, l.id ASC'
+        );
         $stmt->execute(['owner' => $ownerId]);
 
         return array_map($this->cast(...), $stmt->fetchAll());
     }
 
+    public function countForOwner(int $ownerId): int
+    {
+        $stmt = $this->pdo->prepare('SELECT COUNT(*) FROM todo_lists WHERE owner_id = :owner');
+        $stmt->execute(['owner' => $ownerId]);
+
+        return (int) $stmt->fetchColumn();
+    }
+
     /**
      * @return TodoListRow|null
      */