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/slides/IntroPresenterSlide.tsx

@@ -53,11 +53,11 @@ export default function IntroPresenterSlide({ lang, onStartPresenter, isPresenti
         transition={{ delay: 0.3, duration: 0.5 }}
       >
         <h1 className="text-4xl md:text-5xl font-bold mb-3">
-          <GradientText>{isDE ? 'KI-Praesentator' : 'AI Presenter'}</GradientText>
+          <GradientText>{isDE ? 'KI-Präsentator' : 'AI Presenter'}</GradientText>
         </h1>
         <p className="text-lg text-white/60 max-w-lg mx-auto mb-8">
           {isDE
-            ? 'Ihr persoenlicher KI-Guide durch das BreakPilot ComplAI Pitch Deck. 15 Minuten, alle Fakten, jederzeit unterbrechbar.'
+            ? 'Ihr persönlicher KI-Guide durch das BreakPilot ComplAI Pitch Deck. 15 Minuten, alle Fakten, jederzeit unterbrechbar.'
             : 'Your personal AI guide through the BreakPilot ComplAI pitch deck. 15 minutes, all facts, interruptible at any time.'}
         </p>
       </motion.div>
@@ -79,12 +79,12 @@ export default function IntroPresenterSlide({ lang, onStartPresenter, isPresenti
             {isPresenting ? (
               <>
                 <Pause className="w-5 h-5" />
-                {isDE ? 'Praesentation laeuft...' : 'Presentation running...'}
+                {isDE ? 'Präsentation läuft...' : 'Presentation running...'}
               </>
             ) : (
               <>
                 <Play className="w-5 h-5" />
-                {isDE ? 'Praesentation starten' : 'Start Presentation'}
+                {isDE ? 'Präsentation starten' : 'Start Presentation'}
               </>
             )}
           </span>
@@ -108,7 +108,7 @@ export default function IntroPresenterSlide({ lang, onStartPresenter, isPresenti
         </div>
         <div className="flex items-center gap-2">
           <span className="px-1.5 py-0.5 bg-white/10 rounded text-xs font-mono">ESC</span>
-          <span>{isDE ? 'Slide-Uebersicht' : 'Slide Overview'}</span>
+          <span>{isDE ? 'Slide-Übersicht' : 'Slide Overview'}</span>
         </div>
       </motion.div>
     </div>