feat(ocr-pipeline): improve LLM review UI + add reconstruction step

StepLlmReview: Show full vocab table with image overlay, row-level
status tracking (pending/active/reviewed/corrected/skipped), and
auto-scroll during SSE streaming. Load previous results on mount.

StepReconstruction: New step 7 with editable text fields at original
bbox positions over dewarped image. Zoom controls, tab navigation,
color-coded columns, save to backend.

Backend: Add POST /sessions/{id}/reconstruction endpoint.

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

klausur-service/backend/ocr_pipeline_api.py

@@ -1559,6 +1559,70 @@ async def apply_llm_corrections(session_id: str, request: Request):
     }
 
 
+@router.post("/sessions/{session_id}/reconstruction")
+async def save_reconstruction(session_id: str, request: Request):
+    """Save edited cell texts from reconstruction step."""
+    session = await get_session_db(session_id)
+    if not session:
+        raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
+
+    word_result = session.get("word_result")
+    if not word_result:
+        raise HTTPException(status_code=400, detail="No word result found")
+
+    body = await request.json()
+    cell_updates = body.get("cells", [])
+
+    if not cell_updates:
+        await update_session_db(session_id, current_step=7)
+        return {"session_id": session_id, "updated": 0}
+
+    # Build update map: cell_id -> new text
+    update_map = {c["cell_id"]: c["text"] for c in cell_updates}
+
+    # Update cells
+    cells = word_result.get("cells", [])
+    updated_count = 0
+    for cell in cells:
+        if cell["cell_id"] in update_map:
+            cell["text"] = update_map[cell["cell_id"]]
+            cell["status"] = "edited"
+            updated_count += 1
+
+    word_result["cells"] = cells
+
+    # Also update vocab_entries if present
+    entries = word_result.get("vocab_entries") or word_result.get("entries") or []
+    if entries:
+        # Map cell_id pattern "R{row}_C{col}" to entry fields
+        for entry in entries:
+            row_idx = entry.get("row_index", -1)
+            # Check each field's cell
+            for col_idx, field_name in enumerate(["english", "german", "example"]):
+                cell_id = f"R{row_idx:02d}_C{col_idx}"
+                # Also try without zero-padding
+                cell_id_alt = f"R{row_idx}_C{col_idx}"
+                new_text = update_map.get(cell_id) or update_map.get(cell_id_alt)
+                if new_text is not None:
+                    entry[field_name] = new_text
+
+        word_result["vocab_entries"] = entries
+        if "entries" in word_result:
+            word_result["entries"] = entries
+
+    await update_session_db(session_id, word_result=word_result, current_step=7)
+
+    if session_id in _cache:
+        _cache[session_id]["word_result"] = word_result
+
+    logger.info(f"Reconstruction saved for session {session_id}: {updated_count} cells updated")
+
+    return {
+        "session_id": session_id,
+        "updated": updated_count,
+    }
+
+
 async def _get_rows_overlay(session_id: str) -> Response:
     """Generate dewarped image with row bands drawn on it."""
     session = await get_session_db(session_id)