feat(pitch-deck): make OVH DE TTS opt-in via OVH_TTS_ENABLED_DE env var

Without the flag, German routes to the compliance TTS service which uses
Edge TTS (de-DE-ConradNeural) with Piper as fallback — easier to A/B
between OVH and compliance/Edge TTS without code changes.

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

pitch-deck/app/api/presenter/tts/route.ts

@@ -6,13 +6,16 @@ const LITELLM_API_KEY = process.env.LITELLM_API_KEY || ''
 
 // OVH AI Endpoints TTS via the LiteLLM passthrough.
 // Path on the LiteLLM side: /tts-ovh/audio/*  →  https://nvr-tts-<lang>.endpoints.kepler.ai.cloud.ovh.net/api/*
+// OVH DE is opt-in: set OVH_TTS_ENABLED_DE=true to activate.
+// When disabled, German falls through to the compliance TTS service (Edge TTS → Piper).
 const OVH_TTS = {
-  de: {
+  de: process.env.OVH_TTS_ENABLED_DE === 'true'
+    ? {
         url: process.env.OVH_TTS_URL_DE || `${LITELLM_URL}/tts-ovh/audio/v1/tts/text_to_audio`,
-    // German only exposes a male voice; note the hyphen separator (EN uses dots).
         voice: process.env.OVH_TTS_VOICE_DE || 'German-DE-Male-1',
         languageCode: 'de-DE',
-  },
+      }
+    : null,
   // Enable by setting OVH_TTS_URL_EN (e.g. pointing at a second LiteLLM
   // passthrough that targets nvr-tts-en-us). Keeps EN on the old path until set.
   en: process.env.OVH_TTS_URL_EN
@@ -22,7 +25,7 @@ const OVH_TTS = {
         languageCode: 'en-US',
       }
     : null,
-} as const
+}
 
 const SAMPLE_RATE_HZ = parseInt(process.env.OVH_TTS_SAMPLE_RATE || '16000', 10)