Fix scanner service worker CDN URL and clean up MeilisearchConsistencyCommand

- Replace unpkg.com with cdn.jsdelivr.net in sw.js cache list
- Fix sw.js scope to /scanner/
- Remove unused $indexes parameter from checkAllIndexes()
- Extract duplicated " [%s] Index missing" literal to INDEX_MISSING_MSG constant

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/scanner/sw.js

@@ -1,7 +1,7 @@
 const CACHE_NAME = 'scanner-v1';
 const ASSETS = [
-    '/scanner',
-    'https://unpkg.com/html5-qrcode@2.3.8/html5-qrcode.min.js',
+    '/scanner/',
+    'https://cdn.jsdelivr.net/npm/html5-qrcode@2.3.8/html5-qrcode.min.js',
 ];
 
 self.addEventListener('install', (e) => {