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>

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

@@ -57,6 +57,10 @@ export function StepGridReview({ sessionId, onNext, saveRef }: StepGridReviewPro
     toggleSelectedBold,
     autoCorrectColumnPatterns,
     setCellColor,
+    ipaMode,
+    setIpaMode,
+    syllableMode,
+    setSyllableMode,
   } = useGridEditor(sessionId)
 
   const [showImage, setShowImage] = useState(true)
@@ -283,11 +287,15 @@ export function StepGridReview({ sessionId, onNext, saveRef }: StepGridReviewPro
           canUndo={canUndo}
           canRedo={canRedo}
           showOverlay={false}
+          ipaMode={ipaMode}
+          syllableMode={syllableMode}
           onSave={saveGrid}
           onUndo={undo}
           onRedo={redo}
           onRebuild={buildGrid}
           onToggleOverlay={() => setShowImage(!showImage)}
+          onIpaModeChange={setIpaMode}
+          onSyllableModeChange={setSyllableMode}
         />
       </div>