feat: apply IPA phonetic correction in build-grid combo mode

fix_cell_phonetics was only called in the OCR pipeline endpoints
(/words, /cells) but not in the combo mode (build-grid / ocr-overlay).
Garbled IPA like [teist] is now corrected to [teɪst] using the
IPA dictionary, same as in the pipeline.

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

klausur-service/backend/grid_editor_api.py

@@ -21,6 +21,7 @@ from fastapi import APIRouter, HTTPException, Request
 
 from cv_box_detect import detect_boxes, split_page_into_zones
 from cv_color_detect import detect_word_colors, recover_colored_text
+from cv_ocr_engines import fix_cell_phonetics
 from cv_words_first import _cluster_rows, _build_cells
 from ocr_pipeline_session_store import (
     get_session_db,
@@ -970,6 +971,11 @@ async def build_grid(session_id: str):
             if ")" in text and "(" not in text:
                 cell["text"] = "(" + text
 
+    # 5c. IPA phonetic correction — replace garbled OCR phonetics with
+    # correct IPA from the dictionary (same as in the OCR pipeline).
+    all_cells = [cell for z in zones_data for cell in z.get("cells", [])]
+    fix_cell_phonetics(all_cells, pronunciation="british")
+
     duration = time.time() - t0
 
     # 6. Build result