fix(stability-agent): run as uid 1000 with docker group access

stability-agent had no USER instruction and no user: in compose, running
as root and writing root-owned files to /opt/homelab bind-mount.

- Dockerfile: add useradd -m -u 1000 homelab + USER homelab
- docker-compose.yml: add user: "1000:1000" and group_add: ["999"]
  (GID 999 = docker group on VPS) to retain docker.sock:ro access

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/control-plane/Dockerfile

@@ -20,4 +20,5 @@ ENV RUNTIME_PATH=/opt/homelab
 ENV PYTHONUNBUFFERED=1
 
 # Default command (will be overridden in docker-compose)
+USER homelab
 CMD ["python", "src/operator_ui.py"]

services/control-plane/docker-compose.yml

@@ -56,6 +56,9 @@ services:
   executor:
     build: .
     container_name: control-plane-executor
+    user: "1000:1000"
+    group_add:
+      - "999"
     command: python src/executor.py
     volumes:
       - /opt/homelab:/opt/homelab

services/node-agent/Dockerfile

@@ -14,8 +14,11 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 # pyyaml      : may be needed for reading host config snippets
 RUN pip install --no-cache-dir "docker>=6.0" psutil pyyaml
 
+RUN useradd -m -u 1000 homelab
+
 COPY src/ /app/src/
 
 ENV PYTHONUNBUFFERED=1
 
+USER homelab
 CMD ["python", "src/node_agent.py"]

services/node-agent/docker-compose.yml

@@ -2,6 +2,9 @@ services:
   node-agent:
     build: .
     container_name: node-agent
+    user: "1000:1000"
+    group_add:
+      - "999"
     restart: unless-stopped
 
     environment:

services/stability-agent/Dockerfile

@@ -5,6 +5,8 @@ WORKDIR /app
 # No extra dependencies needed beyond standard library for the current script
 # But we might need them if we decide to use libraries later.
 
+RUN useradd -m -u 1000 homelab
+
 COPY src/stability_agent.py .
 COPY healthcheck.sh .
 RUN chmod +x healthcheck.sh
@@ -12,5 +14,5 @@ RUN chmod +x healthcheck.sh
 # Create the expected directories
 RUN mkdir -p /opt/homelab/state /opt/homelab/events
 
-# Run the agent
+USER homelab
 CMD ["python", "stability_agent.py"]

services/stability-agent/docker-compose.yml

@@ -2,6 +2,9 @@ services:
   stability-agent:
     build: .
     container_name: stability-agent
+    user: "1000:1000"
+    group_add:
+      - "999"
     restart: unless-stopped
     volumes:
       - /opt/homelab:/opt/homelab