Add Ansicht step (Step 12) — read-only page layout preview

New pipeline step showing the reconstructed page with all zones
positioned at their original coordinates:
- Content zones with vocabulary grid cells
- Box zones with colored borders (from structure detection)
- Colspan cells rendered across multiple columns
- Multi-line cells (bullets) with pre-wrap whitespace
- Toggle to overlay original scan image at 15% opacity
- Proportionally scaled to viewport width
- Pure CSS positioning (no canvas/Fabric.js)

Pipeline: 14 steps (0-13), Ground Truth moved to Step 13.
Added colspan field to GridEditorCell type.

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

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

@@ -17,6 +17,7 @@ import { StepGridBuild } from '@/components/ocr-kombi/StepGridBuild'
 import { StepGridReview } from '@/components/ocr-kombi/StepGridReview'
 import { StepGutterRepair } from '@/components/ocr-kombi/StepGutterRepair'
 import { StepBoxGridReview } from '@/components/ocr-kombi/StepBoxGridReview'
+import { StepAnsicht } from '@/components/ocr-kombi/StepAnsicht'
 import { StepGroundTruth } from '@/components/ocr-kombi/StepGroundTruth'
 import { useKombiPipeline } from './useKombiPipeline'
 
@@ -100,6 +101,8 @@ function OcrKombiContent() {
       case 11:
         return <StepBoxGridReview sessionId={sessionId} onNext={handleNext} />
       case 12:
+        return <StepAnsicht sessionId={sessionId} onNext={handleNext} />
+      case 13:
         return (
           <StepGroundTruth
             sessionId={sessionId}