feat: Dewarp-Korrektur als Schritt 2 in OCR Pipeline (7 Schritte)

Implementiert Buchwoelbungs-Entzerrung mit zwei Methoden:
- Methode A: Vertikale-Kanten-Analyse (Sobel + Polynom 2. Grades)
- Methode B: Textzeilen-Baseline (Tesseract + Baseline-Kruemmung)
Beste Methode wird automatisch gewaehlt, manueller Slider (-3 bis +3).

Backend: 3 neue Endpoints (auto/manual dewarp, ground truth)
Frontend: StepDewarp + DewarpControls, Pipeline von 6 auf 7 Schritte

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

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

@@ -4,6 +4,7 @@ import { useState } from 'react'
 import { PagePurpose } from '@/components/common/PagePurpose'
 import { PipelineStepper } from '@/components/ocr-pipeline/PipelineStepper'
 import { StepDeskew } from '@/components/ocr-pipeline/StepDeskew'
+import { StepDewarp } from '@/components/ocr-pipeline/StepDewarp'
 import { StepColumnDetection } from '@/components/ocr-pipeline/StepColumnDetection'
 import { StepWordRecognition } from '@/components/ocr-pipeline/StepWordRecognition'
 import { StepCoordinates } from '@/components/ocr-pipeline/StepCoordinates'
@@ -13,6 +14,7 @@ import { PIPELINE_STEPS, type PipelineStep } from './types'
 
 export default function OcrPipelinePage() {
   const [currentStep, setCurrentStep] = useState(0)
+  const [sessionId, setSessionId] = useState<string | null>(null)
   const [steps, setSteps] = useState<PipelineStep[]>(
     PIPELINE_STEPS.map((s, i) => ({
       ...s,
@@ -39,19 +41,26 @@ export default function OcrPipelinePage() {
     }
   }
 
+  const handleDeskewComplete = (sid: string) => {
+    setSessionId(sid)
+    handleNext()
+  }
+
   const renderStep = () => {
     switch (currentStep) {
       case 0:
-        return <StepDeskew onNext={handleNext} />
+        return <StepDeskew onNext={handleDeskewComplete} />
       case 1:
-        return <StepColumnDetection />
+        return <StepDewarp sessionId={sessionId} onNext={handleNext} />
       case 2:
-        return <StepWordRecognition />
+        return <StepColumnDetection />
       case 3:
-        return <StepCoordinates />
+        return <StepWordRecognition />
       case 4:
-        return <StepReconstruction />
+        return <StepCoordinates />
       case 5:
+        return <StepReconstruction />
+      case 6:
         return <StepGroundTruth />
       default:
         return null