Add IPA and syllable mode toggles, fix false IPA on German documents

Backend: Remove en_col_type fallback heuristic (longest avg text) that
incorrectly identified German columns as English. IPA now only applied
when OCR bracket patterns are actually found. Add ipa_mode (auto/all/none)
and syllable_mode (auto/all/none) query params to build-grid API.

Frontend: Add IPA and Silben dropdown selects to GridToolbar. Modes
are passed as query params on rebuild. Auto = current smart detection,
All = force for all words, Aus = skip entirely.

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

klausur-service/backend/cv_syllable_detect.py

@@ -194,6 +194,8 @@ def insert_syllable_dividers(
     zones_data: List[Dict],
     img_bgr: np.ndarray,
     session_id: str,
+    *,
+    force: bool = False,
 ) -> int:
     """Insert pipe syllable dividers into dictionary cells.
 
@@ -204,6 +206,10 @@ def insert_syllable_dividers(
     OCR.  This guards against pages with zero pipe characters (the primary
     guard — article_col_index — is checked at the call site).
 
+    Args:
+        force: If True, skip the pipe-ratio pre-check and syllabify all
+            content words regardless of whether the original has pipe dividers.
+
     Returns the number of cells modified.
     """
     hyph_de, hyph_en = _get_hyphenators()
@@ -215,24 +221,25 @@ def insert_syllable_dividers(
     # Real dictionary pages with printed syllable dividers will have OCR-
     # detected pipes in many cells.  Pages without syllable dividers will
     # have zero — skip those to avoid false syllabification.
-    total_col_cells = 0
-    cells_with_pipes = 0
-    for z in zones_data:
-        for cell in z.get("cells", []):
-            if cell.get("col_type", "").startswith("column_"):
-                total_col_cells += 1
-                if "|" in cell.get("text", ""):
-                    cells_with_pipes += 1
+    if not force:
+        total_col_cells = 0
+        cells_with_pipes = 0
+        for z in zones_data:
+            for cell in z.get("cells", []):
+                if cell.get("col_type", "").startswith("column_"):
+                    total_col_cells += 1
+                    if "|" in cell.get("text", ""):
+                        cells_with_pipes += 1
 
-    if total_col_cells > 0:
-        pipe_ratio = cells_with_pipes / total_col_cells
-        if pipe_ratio < 0.01:
-            logger.info(
-                "build-grid session %s: skipping syllable insertion — "
-                "only %.1f%% of cells have existing pipes (need >=1%%)",
-                session_id, pipe_ratio * 100,
-            )
-            return 0
+        if total_col_cells > 0:
+            pipe_ratio = cells_with_pipes / total_col_cells
+            if pipe_ratio < 0.01:
+                logger.info(
+                    "build-grid session %s: skipping syllable insertion — "
+                    "only %.1f%% of cells have existing pipes (need >=1%%)",
+                    session_id, pipe_ratio * 100,
+                )
+                return 0
 
     insertions = 0
     for z in zones_data: