feat(comfyui): add local image-gen service (#41)

Adds the comfyui service (yurisasc/comfyui-rocm7.1, gfx1201-tuned for the
R9700) on the ai-stack network, published on host port 8138 for a planned
external nginx route to comfy.home. Resolves PUID/PGID/VIDEO_GID/RENDER_GID
from the host in scripts/update.sh, same pattern as SEARXNG_LAN_IP.

OmniRoute provider registration (http://comfyui:8188) is still the same
manual dashboard/POST-/api/providers flow already used for llama-server —
not scripted, per docs/proxy-key-onboarding.md.

Part of wayfinder map #38.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015zCwaWJQuKgXDUfRPBqDS7

.env.example

@@ -87,3 +87,12 @@ OMNIROUTE_WS_BRIDGE_SECRET=
 # needs a dashboard login session, not a static bearer key (see issue #37).
 # Mint them by hand in the dashboard, add a KEY=value line here per workload
 # as you onboard one. See docs/proxy-key-onboarding.md.
+
+# --- ComfyUI (local image generation, see issue #38 wayfinder map) ---
+# yurisasc/comfyui-rocm7.1 manages GPU-group access via these GID/UID env
+# vars rather than relying solely on docker-compose.yml's group_add.
+# Resolved automatically from the host by ./scripts/update.sh — leave blank.
+COMFYUI_PUID=
+COMFYUI_PGID=
+COMFYUI_VIDEO_GID=
+COMFYUI_RENDER_GID=