feat(presenter): add browser TTS (Web Speech API) + fix German umlauts

- Integrate Web Speech API into usePresenterMode for text-to-speech
- Speech-driven paragraph advancement (falls back to timer if TTS unavailable)
- TTS toggle button (Volume2/VolumeX) in PresenterOverlay
- Chrome keepAlive workaround for long speeches
- Voice selection: prefers premium/neural voices, falls back to any matching lang
- Fix all German umlauts across presenter-script, presenter-faq, i18n, route.ts

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

pitch-deck/components/presenter/PresenterOverlay.tsx

@@ -1,7 +1,7 @@
 'use client'
 
 import { motion, AnimatePresence } from 'framer-motion'
-import { Play, Pause, Square, SkipForward } from 'lucide-react'
+import { Play, Pause, Square, SkipForward, Volume2, VolumeX } from 'lucide-react'
 import { Language } from '@/lib/types'
 import { PresenterState } from '@/lib/presenter/types'
 import { SLIDE_ORDER } from '@/lib/hooks/useSlideNavigation'
@@ -18,6 +18,10 @@ interface PresenterOverlayProps {
   onResume: () => void
   onStop: () => void
   onSkip: () => void
+  isSpeaking?: boolean
+  ttsAvailable?: boolean
+  ttsEnabled?: boolean
+  onToggleTts?: () => void
 }
 
 export default function PresenterOverlay({
@@ -31,6 +35,10 @@ export default function PresenterOverlay({
   onResume,
   onStop,
   onSkip,
+  isSpeaking,
+  ttsAvailable,
+  ttsEnabled = true,
+  onToggleTts,
 }: PresenterOverlayProps) {
   const i = t(lang)
   const slideName = i.slideNames[currentIndex] || SLIDE_ORDER[currentIndex] || ''
@@ -79,11 +87,32 @@ export default function PresenterOverlay({
 
                   {/* Controls */}
                   <div className="flex items-center gap-1.5">
+                    {/* TTS toggle */}
+                    {ttsAvailable && onToggleTts && (
+                      <button
+                        onClick={onToggleTts}
+                        className={`w-7 h-7 rounded-full flex items-center justify-center transition-colors ${
+                          ttsEnabled
+                            ? 'bg-indigo-500/30 hover:bg-indigo-500/50'
+                            : 'bg-white/10 hover:bg-white/20'
+                        }`}
+                        title={lang === 'de'
+                          ? (ttsEnabled ? 'Stimme ausschalten' : 'Stimme einschalten')
+                          : (ttsEnabled ? 'Mute voice' : 'Enable voice')}
+                      >
+                        {ttsEnabled ? (
+                          <Volume2 className={`w-3.5 h-3.5 ${isSpeaking ? 'text-indigo-300' : 'text-white/60'}`} />
+                        ) : (
+                          <VolumeX className="w-3.5 h-3.5 text-white/40" />
+                        )}
+                      </button>
+                    )}
+
                     <button
                       onClick={onSkip}
                       className="w-7 h-7 rounded-full bg-white/10 flex items-center justify-center
                         hover:bg-white/20 transition-colors"
-                      title={lang === 'de' ? 'Naechste Folie' : 'Next slide'}
+                      title={lang === 'de' ? 'Nächste Folie' : 'Next slide'}
                     >
                       <SkipForward className="w-3.5 h-3.5 text-white/60" />
                     </button>
@@ -138,7 +167,7 @@ export default function PresenterOverlay({
                 {/* State message */}
                 {state === 'paused' && (
                   <p className="text-xs text-yellow-400/60 mt-1">
-                    {lang === 'de' ? 'Pausiert — stellen Sie eine Frage oder druecken Sie Play' : 'Paused — ask a question or press play'}
+                    {lang === 'de' ? 'Pausiert — stellen Sie eine Frage oder drücken Sie Play' : 'Paused — ask a question or press play'}
                   </p>
                 )}
                 {state === 'answering' && (
@@ -148,7 +177,7 @@ export default function PresenterOverlay({
                 )}
                 {state === 'resuming' && (
                   <p className="text-xs text-indigo-400/60 mt-1">
-                    {lang === 'de' ? 'Setze Praesentation fort...' : 'Resuming presentation...'}
+                    {lang === 'de' ? 'Setze Präsentation fort...' : 'Resuming presentation...'}
                   </p>
                 )}
               </div>