chore(ocr): add opencv-python-headless, libglib2.0-0, and CLAHE env vars

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ocr-service/Dockerfile

@@ -3,10 +3,12 @@ FROM python:3.11.9-slim
 WORKDIR /app
 
 # curl for healthcheck; libgomp1 for PyTorch CPU threading; libvips for kraken PDF support
+# libglib2.0-0 is required by opencv-python-headless on Debian slim
 RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     libgomp1 \
     libvips42 \
+    libglib2.0-0 \
     && rm -rf /var/lib/apt/lists/*
 
 # PyTorch CPU-only — separate layer; the whl/cpu index strips all CUDA variants (~2 GB saved)

ocr-service/requirements.txt

@@ -8,3 +8,4 @@ pillow>=10.2.0,<11.0.0
 pypdfium2==4.30.0
 pyvips>=2.2.0
 httpx==0.28.1
+opencv-python-headless==4.11.0.86