Support a remote ComfyUI via a .env config file

- run.sh / run.ps1: load an optional .env for host-specific env vars
- .env.example + docs: ComfyUI can run on another host (ROUTER_COMFYUI)
- .gitignore: .env

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,13 @@
+# Copy to `.env` (gitignored) for host-specific overrides. run.sh / run.ps1 load it.
+# Only set what you need — every value has a sane default in router.py.
+
+# ComfyUI image generation — point at wherever ComfyUI runs (another box is fine):
+ROUTER_COMFYUI=http://comfyui-host.example:8188
+ROUTER_COMFY_CHECKPOINT=your_model.safetensors
+
+# Bind / networking (defaults shown):
+# ROUTER_HOST=0.0.0.0
+# ROUTER_OLLAMA=http://127.0.0.1:11434
+
+# Audio model for /v1/audio/* (must have 'audio' capability):
+# ROUTER_AUDIO_MODEL=gemma4:e4b