feat: podcast demo mode with ALWRITY_ENABLED_FEATURES support

- Add ALWRITY_ENABLED_FEATURES env var for feature gating
- Podcast-only mode: skip LLM bootstrap, scheduler, persona services
- Enhance video generation prompt with scene context, analysis, narration
- Add voice cloning support via custom_voice_id in WaveSpeed
- Add text-to-speech for research results (browser speechSynthesis)
- Fix render queue to sync images from script phase
- Add WaveSpeed LLM pricing (gpt-oss-120b)
- Fix podcast bible generation error handling
- Refactor RouterManager for feature-based router loading

backend/alwrity_utils/router_manager.py

@@ -116,6 +116,10 @@ class RouterManager:
         if "all" in enabled_features:
             return True
         
+        # Skip core routers in podcast-only mode (they require non-podcast features)
+        if enabled_features == {"podcast"}:
+            return False
+        
         # If no required features specified, include by default
         if not required_features:
             return True