Remove A/B testing toggles from studio-v2 (customer frontend)

Dev-only toggles belong in admin-lehrer (port 3002) only.
The customer frontend runs the pipeline with optimal defaults
and shows only the finished results.

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

studio-v2/app/vocab-worksheet/useVocabWorksheet.ts

@@ -868,7 +868,6 @@ export function useVocabWorksheet(): VocabWorksheetHook {
     processingErrors, successfulPages, failedPages, currentlyProcessingPage,
     // OCR settings
     ocrPrompts, showSettings, setShowSettings,
-    ocrEnhance, setOcrEnhance, ocrMaxCols, setOcrMaxCols, ocrMinConf, setOcrMinConf,
     // QR
     showQRModal, setShowQRModal, uploadSessionId,
     mobileUploadedFiles, selectedMobileFile, setSelectedMobileFile, setMobileUploadedFiles,