feat(ocr-pipeline): British/American IPA pronunciation choice

- Integrate Britfone dictionary (MIT, 15k British English IPA entries)
- Add pronunciation parameter: 'british' (default) or 'american'
- British uses Britfone (Received Pronunciation), falls back to CMU
- American uses eng_to_ipa/CMU, falls back to Britfone
- Frontend: dropdown to switch pronunciation, default = British
- API: ?pronunciation=british|american query parameter

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

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

@@ -34,6 +34,7 @@ export function StepWordRecognition({ sessionId, onNext, goToStep }: StepWordRec
   const [mode, setMode] = useState<'overview' | 'labeling'>('overview')
   const [ocrEngine, setOcrEngine] = useState<'auto' | 'tesseract' | 'rapid'>('auto')
   const [usedEngine, setUsedEngine] = useState<string>('')
+  const [pronunciation, setPronunciation] = useState<'british' | 'american'>('british')
 
   const enRef = useRef<HTMLInputElement>(null)
 
@@ -73,7 +74,7 @@ export function StepWordRecognition({ sessionId, onNext, goToStep }: StepWordRec
     setDetecting(true)
     setError(null)
     try {
-      const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/words?engine=${eng}`, {
+      const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/words?engine=${eng}&pronunciation=${pronunciation}`, {
         method: 'POST',
       })
       if (!res.ok) {
@@ -538,6 +539,16 @@ export function StepWordRecognition({ sessionId, onNext, goToStep }: StepWordRec
               <option value="tesseract">Tesseract</option>
             </select>
 
+            {/* Pronunciation selector */}
+            <select
+              value={pronunciation}
+              onChange={(e) => setPronunciation(e.target.value as 'british' | 'american')}
+              className="px-2 py-1.5 text-xs border rounded-lg dark:bg-gray-700 dark:border-gray-600"
+            >
+              <option value="british">Britisch (RP)</option>
+              <option value="american">Amerikanisch</option>
+            </select>
+
             <button
               onClick={() => runAutoDetection()}
               disabled={detecting}