Move word-study helpers into utils/wordStudy

Strong's dictionary loaders, lexicon lookup, gloss helpers, cross-ref
formatting, and speech move out of App. Dictionaries are now cached at
module level (still one download per visit), and a failed download is no
longer cached forever, so the next lookup retries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/App.test.jsx

@@ -2,6 +2,7 @@ import { render, screen, fireEvent, waitFor, within } from '@testing-library/rea
 import userEvent from '@testing-library/user-event';
 import { vi, beforeEach, afterEach, describe, test, expect } from 'vitest';
 import App from './App';
+import { resetLexiconCaches } from './utils/wordStudy.js';
 
 // ---------------------------------------------------------------------------
 // Shared mock data
@@ -49,6 +50,7 @@ function buildFetchMock({ chapterData = mockChapterData, greekData = null } = {}
 // ---------------------------------------------------------------------------
 beforeEach(() => {
   localStorage.clear();
+  resetLexiconCaches();
   vi.stubGlobal('fetch', buildFetchMock());
   vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:mock');
   vi.spyOn(URL, 'revokeObjectURL').mockImplementation(() => {});