feat(lobe-chat): stand up Lobe Chat on esh-docker-vm over the LiteLLM gateway

Replacement candidate for the hand-rolled gateway-chat HTML surface, which
the operator does not want to keep improving -- it has already produced two
defects tonight.

Chosen over Open WebUI on weight, measured from the registries rather than
recalled: Lobe 143 MB compressed / 1 layer vs Open WebUI 1,825 MB / 19
layers, a 12.8x difference. Open WebUI was declined in June 2026 on weight
and that still holds; its secondary recorded objection (empty-tools 400
against vLLM) is now moot since strip_empty_tools covers the normal API
path and only missed LiteLLM's built-in playground.

CREDENTIAL POSTURE: deliberately NOT the shared all-agents key, which
reaches the paid GLM/Kimi passthroughs -- a LAN-exposed chat UI holding it
would let anyone reaching the port spend vendor credits from a pool shared
across every project. Minted a scoped LiteLLM virtual key
(key_alias lobe-chat-esh) limited to the 20 free local models, and verified
the scoping BOTH ways: gen answers, glm-5.2 / kimi-k3 / gen-frontier all
return 'key not allowed to access model'. Secrets vaulted, host .env 0600.

Verified from INSIDE the container, not just from the host: /v1/models
returns the fleet seats and a gen round-trip returns 'ok', so the app's own
network path and key both work. Container healthy, / -> 307 -> /chat -> 200.

Documents the open question this deploy exists to answer: whether Lobe's
TTS is ENV-configurable or UI-only. That is the operator's deciding
criterion and is NOT yet established -- Open WebUI has dedicated AUDIO_TTS_*
vars, Lobe documents a shared OPENAI_PROXY_URL which should carry TTS since
LiteLLM serves audio/speech on the same base, but that is inference.

Also records the ext-tts voice foot-gun: unknown voices 404 and can trip
the router cooldown, so the voice must be pinned rather than left at a UI
default.

.gitignore

@@ -39,3 +39,4 @@ graphify-out/*
 # Python bytecode (e.g. from local py_compile of stack wrappers)
 __pycache__/
 *.pyc
+stacks/lobe-chat/.env