feat: enable orchestrator + switch TTS to Edge (Seraphina voice)

- Enable delegation.orchestrator_enabled with max_spawn_depth=2
- Switch TTS from ElevenLabs (paid) to Edge TTS (free)
- Voice: de-DE-SeraphinaMultilingualNeural — friendly, multilingual German female
- No API key required

hosts/m3-hermes/services/hermes-agent.nix

@@ -4,8 +4,8 @@
   inputs,
   ...
 }: let
-  # Edge TTS: Katja — warm, friendly German female voice (free, no API key)
+  # Edge TTS: Seraphina — friendly, multilingual German female voice (free, no API key)
-  edgeVoice = "de-DE-KatjaNeural";
+  edgeVoice = "de-DE-SeraphinaMultilingualNeural";
 
   # Extra Python packages from the container's writable venv layer.
   # matrix-nio is installed via pip in /home/hermes/.venv but the hermes