Initial commit: hardened DeerFlow factory

Vendored deer-flow upstream (bytedance/deer-flow) plus prompt-injection
hardening:

- New deerflow.security package: content_delimiter, html_cleaner,
  sanitizer (8 layers — invisible chars, control chars, symbols, NFC,
  PUA, tag chars, horizontal whitespace collapse with newline/tab
  preservation, length cap)
- New deerflow.community.searx package: web_search, web_fetch,
  image_search backed by a private SearX instance, every external
  string sanitized and wrapped in <<<EXTERNAL_UNTRUSTED_CONTENT>>>
  delimiters
- All native community web providers (ddg_search, tavily, exa,
  firecrawl, jina_ai, infoquest, image_search) replaced with hard-fail
  stubs that raise NativeWebToolDisabledError at import time, so a
  misconfigured tool.use path fails loud rather than silently falling
  back to unsanitized output
- Native client back-doors (jina_client.py, infoquest_client.py)
  stubbed too
- Native-tool tests quarantined under tests/_disabled_native/
  (collect_ignore_glob via local conftest.py)
- Sanitizer Layer 7 fix: only collapse horizontal whitespace, preserve
  newlines and tabs so list/table structure survives
- Hardened runtime config.yaml references only the searx-backed tools
- Factory overlay (backend/) kept in sync with deer-flow tree as a
  reference / source

See HARDENING.md for the full audit trail and verification steps.

deer-flow/backend/Dockerfile

@@ -0,0 +1,87 @@
+# Backend Dockerfile — multi-stage build
+# Stage 1 (builder): compiles native Python extensions with build-essential
+# Stage 2 (dev):     retains toolchain for dev containers (uv sync at startup)
+# Stage 3 (runtime): clean image without compiler toolchain for production
+
+# UV source image (override for restricted networks that cannot reach ghcr.io)
+ARG UV_IMAGE=ghcr.io/astral-sh/uv:0.7.20
+FROM ${UV_IMAGE} AS uv-source
+
+# ── Stage 1: Builder ──────────────────────────────────────────────────────────
+FROM python:3.12-slim-bookworm AS builder
+
+ARG NODE_MAJOR=22
+ARG APT_MIRROR
+ARG UV_INDEX_URL
+
+# Optionally override apt mirror for restricted networks (e.g. APT_MIRROR=mirrors.aliyun.com)
+RUN if [ -n "${APT_MIRROR}" ]; then \
+      sed -i "s|deb.debian.org|${APT_MIRROR}|g" /etc/apt/sources.list.d/debian.sources 2>/dev/null || true; \
+      sed -i "s|deb.debian.org|${APT_MIRROR}|g" /etc/apt/sources.list 2>/dev/null || true; \
+    fi
+
+# Install build tools + Node.js (build-essential needed for native Python extensions)
+RUN apt-get update && apt-get install -y \
+    curl \
+    build-essential \
+    gnupg \
+    ca-certificates \
+    && mkdir -p /etc/apt/keyrings \
+    && curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg \
+    && echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_${NODE_MAJOR}.x nodistro main" > /etc/apt/sources.list.d/nodesource.list \
+    && apt-get update \
+    && apt-get install -y nodejs \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install uv (source image overridable via UV_IMAGE build arg)
+COPY --from=uv-source /uv /uvx /usr/local/bin/
+
+# Set working directory
+WORKDIR /app
+
+# Copy backend source code
+COPY backend ./backend
+
+# Install dependencies with cache mount
+RUN --mount=type=cache,target=/root/.cache/uv \
+    sh -c "cd backend && UV_INDEX_URL=${UV_INDEX_URL:-https://pypi.org/simple} uv sync"
+
+# ── Stage 2: Dev ──────────────────────────────────────────────────────────────
+# Retains compiler toolchain from builder so startup-time `uv sync` can build
+# source distributions in development containers.
+FROM builder AS dev
+
+# Install Docker CLI (for DooD: allows starting sandbox containers via host Docker socket)
+COPY --from=docker:cli /usr/local/bin/docker /usr/local/bin/docker
+
+EXPOSE 8001 2024
+
+CMD ["sh", "-c", "cd backend && PYTHONPATH=. uv run uvicorn app.gateway.app:app --host 0.0.0.0 --port 8001"]
+
+# ── Stage 3: Runtime ──────────────────────────────────────────────────────────
+# Clean image without build-essential — reduces size (~200 MB) and attack surface.
+FROM python:3.12-slim-bookworm
+
+# Copy Node.js runtime from builder (provides npx for MCP servers)
+COPY --from=builder /usr/bin/node /usr/bin/node
+COPY --from=builder /usr/lib/node_modules /usr/lib/node_modules
+RUN ln -s ../lib/node_modules/npm/bin/npm-cli.js /usr/bin/npm \
+    && ln -s ../lib/node_modules/npm/bin/npx-cli.js /usr/bin/npx
+
+# Install Docker CLI (for DooD: allows starting sandbox containers via host Docker socket)
+COPY --from=docker:cli /usr/local/bin/docker /usr/local/bin/docker
+
+# Install uv (source image overridable via UV_IMAGE build arg)
+COPY --from=uv-source /uv /uvx /usr/local/bin/
+
+# Set working directory
+WORKDIR /app
+
+# Copy backend with pre-built virtualenv from builder
+COPY --from=builder /app/backend ./backend
+
+# Expose ports (gateway: 8001, langgraph: 2024)
+EXPOSE 8001 2024
+
+# Default command (can be overridden in docker-compose)
+CMD ["sh", "-c", "cd backend && PYTHONPATH=. uv run --no-sync uvicorn app.gateway.app:app --host 0.0.0.0 --port 8001"]