Move import state into ImportPage; share translation list via hook

The session-list import form, preview, and runEpisodeImport now live in
ImportPage. useAvailableTranslations fetches the translation list once per
visit for both Import and Setup. Drops the never-read importFile state.

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

src/pages/SetupPage.jsx

@@ -1,4 +1,5 @@
 import { useApp } from '../context/AppContext.js';
+import { useAvailableTranslations } from '../hooks/useAvailableTranslations.js';
 import { bookOptions, formatChunkReference } from '../utils/bibleUtils.jsx';
 
 function SetupForm({ setup, availableTranslations, titleEdited, loadingChapter, errorMessage, hideTitle, onField, onTitleChange, onLoad }) {
@@ -83,7 +84,6 @@ export default function SetupPage() {
     headerButtons,
     project,
     setup,
-    availableTranslations,
     titleEdited, setTitleEdited,
     activeChapterIndex, setActiveChapterIndex,
     activeChapter,
@@ -111,6 +111,7 @@ export default function SetupPage() {
     deleteChunk,
     updateProject,
   } = useApp();
+  const availableTranslations = useAvailableTranslations();
 
   const chapterTabs = project?.chapters ?? [];