fix(docker): run as non-root user, use virtualenv (salvage #5811)

- Add gosu for runtime privilege dropping from root to hermes user
- Support HERMES_UID/HERMES_GID env vars for host mount permission matching
- Switch to debian:13.4-slim base image
- Use uv venv instead of pip install --break-system-packages
- Pin uv and gosu multi-stage images with SHA256 digests
- Set PLAYWRIGHT_BROWSERS_PATH to /opt/hermes/.playwright so build-time
  chromium install survives the /opt/data volume mount
- Keep procps for container debugging

Based on work by m0n5t3r in PR #5811. Stripped to hardening-only
changes (non-root, virtualenv, slim base); matrix deps, fonts, xvfb,
and entrypoint playwright download deferred to follow-up.

Dockerfile

@@ -1,27 +1,44 @@
-FROM debian:13.4
+FROM ghcr.io/astral-sh/uv:0.11.6-python3.13-trixie@sha256:b3c543b6c4f23a5f2df22866bd7857e5d304b67a564f4feab6ac22044dde719b AS uv_source
+FROM tianon/gosu:1.19-trixie@sha256:3b176695959c71e123eb390d427efc665eeb561b1540e82679c15e992006b8b9 AS gosu_source
+FROM debian:13.4-slim
 
 # Disable Python stdout buffering to ensure logs are printed immediately
 ENV PYTHONUNBUFFERED=1
 
+# Store Playwright browsers outside the volume mount so the build-time
+# install survives the /opt/data volume overlay at runtime.
+ENV PLAYWRIGHT_BROWSERS_PATH=/opt/hermes/.playwright
+
 # Install system dependencies in one layer, clear APT cache
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-        build-essential nodejs npm python3 python3-pip ripgrep ffmpeg gcc python3-dev libffi-dev procps && \
+        build-essential nodejs npm python3 ripgrep ffmpeg gcc python3-dev libffi-dev procps && \
     rm -rf /var/lib/apt/lists/*
 
+# Non-root user for runtime; UID can be overridden via HERMES_UID at runtime
+RUN useradd -u 10000 -m -d /opt/data hermes
+
+COPY --chmod=0755 --from=gosu_source /gosu /usr/local/bin/
+COPY --chmod=0755 --from=uv_source /usr/local/bin/uv /usr/local/bin/uvx /usr/local/bin/
+
 COPY . /opt/hermes
 WORKDIR /opt/hermes
 
-# Install Python and Node dependencies in one layer, no cache
-RUN pip install --no-cache-dir uv --break-system-packages && \
-    uv pip install --system --break-system-packages --no-cache -e ".[all]" && \
-    npm install --prefer-offline --no-audit && \
+# Install Node dependencies and Playwright as root (--with-deps needs apt)
+RUN npm install --prefer-offline --no-audit && \
     npx playwright install --with-deps chromium --only-shell && \
     cd /opt/hermes/scripts/whatsapp-bridge && \
     npm install --prefer-offline --no-audit && \
     npm cache clean --force
 
-WORKDIR /opt/hermes
+# Hand ownership to hermes user, then install Python deps in a virtualenv
+RUN chown -R hermes:hermes /opt/hermes
+USER hermes
+
+RUN uv venv && \
+    uv pip install --no-cache-dir -e ".[all]"
+
+USER root
 RUN chmod +x /opt/hermes/docker/entrypoint.sh
 
 ENV HERMES_HOME=/opt/data