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/services/startup_health.py

@@ -156,6 +156,12 @@ def _check_production_api_key_loading(
     if deploy_env == "local":
         _record_check(checks, "production_api_key_loading", True, "skipped in local deploy mode")
         return
+    
+    # Also skip in podcast-only mode (no production API keys needed)
+    enabled_features = os.getenv("ALWRITY_ENABLED_FEATURES", "all").strip().lower()
+    if enabled_features == "podcast":
+        _record_check(checks, "production_api_key_loading", True, "skipped in podcast-only mode")
+        return
 
     test_tenant_id = os.getenv("ALWRITY_STARTUP_TEST_TENANT_ID", "").strip()
     if not test_tenant_id: