Add scan quality scoring, column limit, image enhancement (Steps 1-3)

Step 1: scan_quality.py — Laplacian blur + contrast scoring, adjusts
OCR confidence threshold (40 for good scans, 30 for degraded).
Quality report included in API response + shown in frontend.

Step 2: max_columns parameter in cv_words_first.py — limits column
detection to 3 for vocab tables, preventing phantom columns D/E
from degraded OCR fragments.

Step 3: ocr_image_enhance.py — CLAHE contrast + bilateral filter
denoising + unsharp mask, only for degraded scans (gated by
quality score). Pattern from handwriting_htr_api.py.

Frontend: quality info shown in extraction status after processing.
Reprocess button now derives pages from vocabulary data.

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

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

@@ -355,7 +355,7 @@ export function useVocabWorksheet(): VocabWorksheetHook {
     }
   }
 
-  const processSinglePage = async (pageIndex: number, ipa: IpaMode, syllable: SyllableMode): Promise<{ success: boolean; vocabulary: VocabularyEntry[]; error?: string }> => {
+  const processSinglePage = async (pageIndex: number, ipa: IpaMode, syllable: SyllableMode): Promise<{ success: boolean; vocabulary: VocabularyEntry[]; error?: string; scanQuality?: any }> => {
     const API_BASE = getApiBase()
 
     try {
@@ -377,7 +377,7 @@ export function useVocabWorksheet(): VocabWorksheetHook {
         return { success: false, vocabulary: [], error: data.error || `Seite ${pageIndex + 1}: Unbekannter Fehler` }
       }
 
-      return { success: true, vocabulary: data.vocabulary || [] }
+      return { success: true, vocabulary: data.vocabulary || [], scanQuality: data.scan_quality }
     } catch (e) {
       return { success: false, vocabulary: [], error: `Seite ${pageIndex + 1}: ${e instanceof Error ? e.message : 'Netzwerkfehler'}` }
     }
@@ -413,7 +413,10 @@ export function useVocabWorksheet(): VocabWorksheetHook {
         successful.push(pageIndex + 1)
         setSuccessfulPages([...successful])
         setVocabulary(prev => [...prev, ...result.vocabulary])
-        setExtractionStatus(`Seite ${pageIndex + 1} fertig: ${result.vocabulary.length} Vokabeln gefunden`)
+        const qualityInfo = result.scanQuality
+          ? ` | Qualitaet: ${result.scanQuality.quality_pct}%${result.scanQuality.is_degraded ? ' (degradiert!)' : ''}`
+          : ''
+        setExtractionStatus(`Seite ${pageIndex + 1} fertig: ${result.vocabulary.length} Vokabeln gefunden${qualityInfo}`)
       } else {
         failed.push(pageIndex + 1)
         setFailedPages([...failed])
@@ -786,7 +789,9 @@ export function useVocabWorksheet(): VocabWorksheetHook {
 
     ;(async () => {
       const allVocab: VocabularyEntry[] = []
+      let lastQuality: any = null
       for (const pageIndex of pagesToReprocess) {
+        setExtractionStatus(`Verarbeite Seite ${pageIndex + 1}...`)
         try {
           const res = await fetch(`${API_BASE}/api/v1/vocab/sessions/${session.id}/process-single-page/${pageIndex}?ipa_mode=${ipa}&syllable_mode=${syllable}`, {
             method: 'POST',
@@ -796,12 +801,16 @@ export function useVocabWorksheet(): VocabWorksheetHook {
           if (res.ok) {
             const data = await res.json()
             if (data.vocabulary) allVocab.push(...data.vocabulary)
+            if (data.scan_quality) lastQuality = data.scan_quality
           }
         } catch {}
       }
       setVocabulary(allVocab)
       setIsExtracting(false)
-      setExtractionStatus(`${allVocab.length} Vokabeln mit neuen Einstellungen`)
+      const qualityInfo = lastQuality
+        ? ` | Qualitaet: ${lastQuality.quality_pct}%${lastQuality.is_degraded ? ' (degradiert!)' : ''} | Blur: ${lastQuality.blur_score} | Kontrast: ${lastQuality.contrast_score}`
+        : ''
+      setExtractionStatus(`${allVocab.length} Vokabeln mit neuen Einstellungen${qualityInfo}`)
     })()
   }