add docs

Dockerfile

@@ -1,8 +1,11 @@
+# syntax=docker/dockerfile:1
+
 FROM python:3.10-slim
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
-    PIP_NO_CACHE_DIR=1
+    HF_HOME=/root/.cache/huggingface \
+    MODELSCOPE_CACHE=/root/.cache/modelscope
 
 WORKDIR /app
 
@@ -10,11 +13,20 @@ RUN apt-get update \
     && apt-get install -y --no-install-recommends libgl1 libglib2.0-0 \
     && rm -rf /var/lib/apt/lists/*
 
+# Layer 1: Python deps — only rebuilds when pyproject.toml changes.
 COPY pyproject.toml README.md ./
-COPY src ./src
+RUN --mount=type=cache,target=/root/.cache/pip \
+    pip install --upgrade pip \
+    && pip install \
+        "fastapi>=0.115" \
+        "uvicorn[standard]>=0.30" \
+        "python-multipart>=0.0.9" \
+        "pydantic-settings>=2.4" \
+        "openocr-python==0.1.5"
 
-RUN pip install --upgrade pip \
-    && pip install .
+# Layer 2: app code — code changes only rerun this lightweight step.
+COPY src ./src
+RUN pip install --no-deps --no-cache-dir .
 
 EXPOSE 8000