Feat: add Docling parser (#10759)

### What problem does this PR solve?
issue:
#3945
change:
add Docling parser

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

docker/.env

@@ -195,3 +195,4 @@ REGISTER_ENABLED=1
 # COMPOSE_PROFILES=infinity,sandbox
 #    - For OpenSearch:
 # COMPOSE_PROFILES=opensearch,sandbox
+USE_DOCLING=false

docker/entrypoint.sh

@@ -178,6 +178,16 @@ function start_mcp_server() {
         "${MCP_JSON_RESPONSE_FLAG}" &
 }
 
+function ensure_docling() {
+  if [[ "${USE_DOCLING}" == "true" ]]; then
+    if ! python3 -c "import importlib.util,sys; sys.exit(0 if importlib.util.find_spec('docling') else 1)"; then
+      echo "[docling] not found, installing..."
+      python3 -m pip install --no-cache-dir "docling${DOCLING_VERSION:-}"
+    else
+      echo "[docling] already installed, skip."
+    fi
+  fi
+}
 # -----------------------------------------------------------------------------
 # Start components based on flags
 # -----------------------------------------------------------------------------
@@ -203,6 +213,8 @@ if [[ "${ENABLE_MCP_SERVER}" -eq 1 ]]; then
     start_mcp_server
 fi
 
+ensure_docling
+
 if [[ "${ENABLE_TASKEXECUTOR}" -eq 1 ]]; then
     if [[ "${CONSUMER_NO_END}" -gt "${CONSUMER_NO_BEG}" ]]; then
         echo "Starting task executors on host '${HOST_ID}' for IDs in [${CONSUMER_NO_BEG}, ${CONSUMER_NO_END})..."