v0.13.0:3 - proxy /v1/chat/completions through Spark Control to vLLM

Recap Relay dev caught that all audio endpoints route through Spark
Control but chat-completions didn't — clients had to know about both
SC AND the direct vLLM URL on Spark 1. Closes that last gap.

New endpoints:
  POST /v1/chat/completions   — OpenAI-shape, forwards to vLLM on Spark 1
  POST /v1/completions        — legacy OpenAI completions, same path

Implementation (image/app/llm_proxy.py):
  - Dumb forwarder: request body passed through verbatim, response body
    streamed back chunk-by-chunk. No transformation. vLLM already speaks
    the same shape; adding any logic here would just create skew.
  - Streaming: parses body for `stream: true` and uses httpx.AsyncClient
    .stream() + FastAPI StreamingResponse if so. Non-streaming path is
    a simple post-and-return.
  - 30-minute timeout to accommodate large-context completions (default
    httpx 5s would kill anything substantial).
  - On upstream non-200 in streaming mode: emits one SSE `error` event
    so the client's parser doesn't hang on an empty stream forever.
  - On upstream connection error: HTTP 502 with "vllm unreachable" detail.

Now clients can use ONE host for everything:
  POST https://spark-control/api/audio/diarize-chunk
  POST https://spark-control/v1/audio/transcriptions
  POST https://spark-control/v1/chat/completions
  GET  https://spark-control/api/endpoints  (still works for clients that
                                              prefer the direct URLs)

No parakeet container changes. No Reapply patches needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

image/app/server.py

@@ -16,6 +16,7 @@ from .audio_proxy import build_router as build_audio_router
 from .deep_health import DeepHealth
 from .disk import delete_from_disk, probe_disk
 from .download import DownloadManager
+from .llm_proxy import build_router as build_llm_router
 from .hardware import HardwareProbe
 from .health import check_magpie, check_parakeet, check_vllm
 from .models import load_catalog
@@ -64,6 +65,12 @@ app.mount("/static", StaticFiles(directory=_STATIC_DIR), name="static")
 # when Parakeet returns 500, instead of waiting up to 5 min for the periodic probe.
 app.include_router(build_audio_router(settings, deep_health=deep_health))
 
+# OpenAI-compatible LLM proxy: /v1/chat/completions, /v1/completions.
+# Forwards to whatever vLLM is currently running on Spark 1 (per the LLM swap
+# state). Supports SSE streaming when stream=true. Same trusted-host model
+# as the audio proxy — clients only need one URL for everything.
+app.include_router(build_llm_router(settings))
+
 
 @app.get("/", include_in_schema=False)
 async def index() -> FileResponse: