feat: add Excel-like grid editor for OCR overlay (Kombi mode step 6)

Backend: new grid_editor_api.py with build-grid endpoint that detects
bordered boxes, splits page into zones, clusters columns/rows per zone
from Kombi word positions. New DB column grid_editor_result JSONB.

Frontend: GridEditor component with editable HTML tables per zone,
column bold toggle, header row toggle, undo/redo, keyboard navigation
(Tab/Enter/Arrow), image overlay verification, and save/load.

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

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

@@ -11,6 +11,7 @@ import { StepRowDetection } from '@/components/ocr-pipeline/StepRowDetection'
 import { StepWordRecognition } from '@/components/ocr-pipeline/StepWordRecognition'
 import { OverlayReconstruction } from '@/components/ocr-overlay/OverlayReconstruction'
 import { PaddleDirectStep } from '@/components/ocr-overlay/PaddleDirectStep'
+import { GridEditor } from '@/components/grid-editor/GridEditor'
 import { OVERLAY_PIPELINE_STEPS, PADDLE_DIRECT_STEPS, KOMBI_STEPS, DOCUMENT_CATEGORIES, dbStepToOverlayUi, type PipelineStep, type SessionListItem, type DocumentCategory } from './types'
 
 const KLAUSUR_API = '/klausur-api'
@@ -72,13 +73,17 @@ export default function OcrOverlayPage() {
         const m = isKombi ? 'kombi' : 'paddle-direct'
         const baseSteps = isKombi ? KOMBI_STEPS : PADDLE_DIRECT_STEPS
         setMode(m)
+
+        // For Kombi: if grid_editor_result exists, jump to grid editor step (5)
+        const hasGrid = isKombi && data.grid_editor_result
+        const activeStep = hasGrid ? 5 : 4
         setSteps(
           baseSteps.map((s, i) => ({
             ...s,
-            status: i < 4 ? 'completed' : i === 4 ? 'active' : 'pending',
+            status: i < activeStep ? 'completed' : i === activeStep ? 'active' : 'pending',
           })),
         )
-        setCurrentStep(4)
+        setCurrentStep(activeStep)
       } else {
         setMode('pipeline')
         // Map DB step to overlay UI step
@@ -256,6 +261,10 @@ export default function OcrOverlayPage() {
           ) : (
             <PaddleDirectStep sessionId={sessionId} onNext={handleNext} />
           )
+        case 5:
+          return mode === 'kombi' ? (
+            <GridEditor sessionId={sessionId} onNext={handleNext} />
+          ) : null
         default:
           return null
       }
@@ -512,7 +521,7 @@ export default function OcrOverlayPage() {
               : 'text-gray-500 dark:text-gray-400 hover:text-gray-700 dark:hover:text-gray-300'
           }`}
         >
-          Kombi (5 Schritte)
+          Kombi (6 Schritte)
         </button>
       </div>
 

admin-lehrer/app/(admin)/ai/ocr-overlay/types.ts

@@ -70,6 +70,7 @@ export const KOMBI_STEPS: PipelineStep[] = [
   { id: 'dewarp', name: 'Entzerrung', icon: '🔧', status: 'pending' },
   { id: 'crop', name: 'Zuschneiden', icon: '✂️', status: 'pending' },
   { id: 'kombi', name: 'PP-OCRv5 + Tesseract', icon: '🔀', status: 'pending' },
+  { id: 'grid-editor', name: 'Tabelle', icon: '📊', status: 'pending' },
 ]
 
 /** Map from DB step to overlay UI step index */