fix: move Struktur step after OCR so word boxes are available for exclusion

Graphic detection needs word positions to exclude text from the ink mask.
Previously Struktur ran before OCR, causing every word to be detected as
a graphic element. Now:
- Pipeline: Struktur at index 7 (after Wörter)
- Kombi: Struktur at index 5 (after PP-OCRv5+Tesseract, before Tabelle)

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

admin-lehrer/app/(admin)/ai/ocr-pipeline/page.tsx

@@ -92,15 +92,15 @@ export default function OcrPipelinePage() {
       let uiStep = Math.max(0, dbStep - 1)
       const skipSteps = [...(savedDocType?.skip_steps || [])]
 
-      // Sub-sessions: image is already cropped, skip pre-processing + structure steps
-      // Jump directly to columns (UI step 5) unless already further ahead
+      // Sub-sessions: image is already cropped, skip pre-processing steps
+      // Jump directly to columns (UI step 4) unless already further ahead
       const isSubSession = !!data.parent_session_id
-      const SUB_SESSION_SKIP = ['orientation', 'deskew', 'dewarp', 'crop', 'structure']
+      const SUB_SESSION_SKIP = ['orientation', 'deskew', 'dewarp', 'crop']
       if (isSubSession) {
         for (const s of SUB_SESSION_SKIP) {
           if (!skipSteps.includes(s)) skipSteps.push(s)
         }
-        if (uiStep < 5) uiStep = 5 // columns step (now index 5)
+        if (uiStep < 4) uiStep = 4 // columns step (index 4)
       }
 
       setSteps(
@@ -330,10 +330,10 @@ export default function OcrPipelinePage() {
     2: 'Begradigung',
     3: 'Entzerrung',
     4: 'Zuschneiden',
-    5: 'Struktur',
-    6: 'Spalten',
-    7: 'Zeilen',
-    8: 'Woerter',
+    5: 'Spalten',
+    6: 'Zeilen',
+    7: 'Woerter',
+    8: 'Struktur',
     9: 'Korrektur',
     10: 'Rekonstruktion',
     11: 'Validierung',
@@ -373,13 +373,13 @@ export default function OcrPipelinePage() {
       case 3:
         return <StepCrop sessionId={sessionId} onNext={handleCropNext} />
       case 4:
-        return <StepStructureDetection sessionId={sessionId} onNext={handleNext} />
-      case 5:
         return <StepColumnDetection sessionId={sessionId} onNext={handleNext} onBoxSessionsCreated={handleBoxSessionsCreated} />
-      case 6:
+      case 5:
         return <StepRowDetection sessionId={sessionId} onNext={handleNext} />
-      case 7:
+      case 6:
         return <StepWordRecognition sessionId={sessionId} onNext={handleNext} goToStep={goToStep} />
+      case 7:
+        return <StepStructureDetection sessionId={sessionId} onNext={handleNext} />
       case 8:
         return <StepLlmReview sessionId={sessionId} onNext={handleNext} />
       case 9: