fix: always re-run structure detection instead of using cached result

The frontend was checking for an existing structure_result and reusing
it, which meant the backend fix (passing word_boxes to graphic detection)
never had a chance to run on existing sessions.

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

admin-lehrer/components/ocr-pipeline/StepStructureDetection.tsx

@@ -36,18 +36,7 @@ export function StepStructureDetection({ sessionId, onNext }: StepStructureDetec
       setError(null)
 
       try {
-        // Check if session already has structure result
-        const sessionRes = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}`)
-        if (sessionRes.ok) {
-          const sessionData = await sessionRes.json()
-          if (sessionData.structure_result) {
-            setResult(sessionData.structure_result)
-            setOverlayTs(Date.now())
-            setDetecting(false)
-            return
-          }
-        }
-
+        // Always re-run detection to pick up latest word_result from OCR step
         const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/detect-structure`, {
           method: 'POST',
         })