Migrate Open WebUI and coding CLIs to the AI proxy (resolves #15)

Open WebUI now points at litellm instead of llama-server directly, using a
provisioned virtual key. llama-server's host port is dropped (internal-only
on the ai-stack network) since the proxy is the only intended entry point
now. docs/coding-cli-setup.md repointed at the proxy's endpoints/ports with
per-CLI virtual keys instead of the old shared dummy key.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

litellm-config.yaml

@@ -1,7 +1,10 @@
 model_list:
   - model_name: qwen3.8-27b-local
     litellm_params:
-      model: openai/${LLAMA_MODEL_FILE:-Qwen3.8-27B-UD-Q4_K_XL.gguf}
+      # Static name — llama.cpp serves whatever model it loaded regardless of
+      # what's requested here; this string isn't shell-expanded (this file
+      # isn't docker-compose.yml, .env vars don't reach it).
+      model: openai/qwen3.8-27b-local
       api_base: http://llama-server:8080/v1
       api_key: local
     model_info: