feat(cefr): CEFR level testing and automated gap ingestion engine (Task 15)

app/static/sw.js

@@ -1,7 +1,7 @@
 // Service Worker for Notes English PWA (Stage 2)
 // Strategy: Cache-first for static assets, Network-first for API calls.
 
-const CACHE_NAME = 'notes-v5.0';
+const CACHE_NAME = 'notes-v5.1';
 const OFFLINE_URL = '/';
 
 const PRECACHE_URLS = [
@@ -13,6 +13,7 @@ const PRECACHE_URLS = [
   '/static/js/modules/dictionary.js',
   '/static/js/modules/srs.js',
   '/static/js/modules/reader.js',
+  '/static/js/modules/cefr.js',
   '/manifest.json',
 ];