fix(flashcards): COLORS перемещён перед IIFE — устранён ReferenceError

const COLORS и let _deckColor объявлены в temporal dead zone во время
вызова init() из IIFE (const не hoisting, function — да). Перемещены
перед IIFE: теперь COLORS инициализирован до первого вызова buildColorPicker().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/flashcards.html

@@ -371,6 +371,15 @@
 <script src="https://cdn.jsdelivr.net/npm/katex@0.16.9/dist/katex.min.js"></script>
 <script src="https://cdn.jsdelivr.net/npm/katex@0.16.9/dist/contrib/auto-render.min.js"></script>
 <script>
+/* ════ Constants & State ════ */
+const COLORS = ['#9B5DE5','#EF476F','#FF9F1C','#06D6E0','#22d399','#3B82F6','#F15BB5','#6B7280'];
+
+let _decks    = [];
+let _curDeck  = null;
+let _cards    = [];
+let _editingDeckId = null;
+let _deckColor = '#9B5DE5';
+
 (async () => {
   /* ── auth ── */
   const { user } = LS.initPage();
@@ -390,15 +399,6 @@
   init();
 })();
 
-/* ════ State ════ */
-let _decks    = [];
-let _curDeck  = null;   // { id, title, color, ... }
-let _cards    = [];     // cards in current deck
-let _editingDeckId = null;
-let _deckColor = '#9B5DE5';
-
-const COLORS = ['#9B5DE5','#EF476F','#FF9F1C','#06D6E0','#22d399','#3B82F6','#F15BB5','#6B7280'];
-
 /* ════ Init ════ */
 async function init() {
   buildColorPicker();