feat(observability): add structured application logging

Emit correlated JSON logs from the API and FunASR services, propagate request IDs to the client, and configure bounded opt-in Docker logging.

Document the host-wide Grafana/Loki query workflow and keep observability deployment ownership outside the application repository.

asr-service/Dockerfile

@@ -2,10 +2,16 @@ FROM python:3.10-slim
 
 ARG DEBIAN_MIRROR=http://deb.debian.org
 ARG PYPI_INDEX_URL=https://pypi.org/simple
+ARG APP_VERSION=0.2.0
+ARG GIT_SHA=unknown
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
-    PIP_NO_CACHE_DIR=1
+    PIP_NO_CACHE_DIR=1 \
+    APP_ENV=lan \
+    APP_VERSION=${APP_VERSION} \
+    GIT_SHA=${GIT_SHA} \
+    LOG_FORMAT=json
 
 RUN sed -i "s|http://deb.debian.org|${DEBIAN_MIRROR}|g" /etc/apt/sources.list.d/debian.sources \
     && apt-get update \
@@ -18,7 +24,7 @@ RUN pip install --index-url "${PYPI_INDEX_URL}" --upgrade pip
 RUN pip install torch==2.8.0 torchaudio==2.8.0 --index-url https://download.pytorch.org/whl/cpu
 RUN pip install --index-url "${PYPI_INDEX_URL}" -r requirements.txt
 
-COPY app.py ./
+COPY app.py logging_config.py ./
 
 EXPOSE 10095
 CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "10095", "--workers", "1", "--no-access-log"]