ops(gpu-health): GPU 서비스 health/smoke 표준화 + synthetic VRAM 피크 가드

PR-GPU-Health-1. 운영 준비성 표준화 PR (모델 성능 개선 아님).

- OCR /smoke endpoint 추가 (160x60 OK PNG in-memory, 200/503 분기, Docker healthcheck 미사용)
- marker /health endpoint 추가 (stt/ocr 동일 시그니처)
- reranker docker-compose healthcheck 추가 (TEI :80/health)
- scripts/gpu_service_smoke.sh: docker exec 표준 점검 (OCR/STT expose-only)
- scripts/gpu_vram_fixture.sh: Mode A sequential + Mode B light overlap + --stress 옵션
- tests/load/fixtures/: synthetic ocr_ok.png / sine_30s.wav / lorem_1p.pdf

OCR 빈 응답 false negative — root cause: ports 미매핑.
결정: ocr-service / stt-service 는 expose-only 유지, 운영 점검은 docker exec 내부 curl 표준.

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

services/marker/server.py

@@ -100,6 +100,11 @@ class ConvertResponse(BaseModel):
     images_truncated: bool = False
 
 
+@app.get("/health")
+def health():
+    return {"status": "ok", "service": "marker-service"}
+
+
 @app.get("/ready")
 async def ready(response: Response):
     """Round 4 #1+#2: Response.status_code 명시 + warmup_error 노출."""

services/ocr/server.py

@@ -4,13 +4,16 @@
 모델은 첫 요청 시 lazy loading.
 """
 
+import asyncio
+import time
 import unicodedata
 from pathlib import Path
 
 import fitz
 import torch
 from fastapi import FastAPI
-from PIL import Image
+from fastapi.responses import JSONResponse
+from PIL import Image, ImageDraw
 
 app = FastAPI()
 
@@ -82,6 +85,30 @@ def ready():
     }
 
 
+@app.get("/smoke")
+async def smoke():
+    """OCR 라운드트립이 예외 없이 완료되는지 운영 verify. Docker healthcheck 미사용."""
+    start = time.monotonic()
+    img = Image.new("RGB", (160, 60), color="white")
+    draw = ImageDraw.Draw(img)
+    draw.text((30, 20), "OK", fill="black")
+    try:
+        loop = asyncio.get_running_loop()
+        await asyncio.wait_for(
+            loop.run_in_executor(None, _ocr_image, img),
+            timeout=20.0,
+        )
+    except asyncio.TimeoutError:
+        return JSONResponse(status_code=503, content={"status": "degraded", "reason": "timeout"})
+    except Exception as exc:
+        return JSONResponse(
+            status_code=503,
+            content={"status": "degraded", "reason": exc.__class__.__name__},
+        )
+    elapsed_ms = int((time.monotonic() - start) * 1000)
+    return {"status": "ok", "service": "ocr-service", "inference": "ok", "elapsed_ms": elapsed_ms}
+
+
 @app.post("/ocr")
 async def ocr_endpoint(body: dict):
     """PDF/이미지 OCR — 페이지 단위 처리 (전체 일괄 로드 금지)"""