fix(fabric): use broadcast subject for NATS capabilities discovery

NATS wildcards (node.*.capabilities.get) only work for subscriptions,
not for publish. Switch to a dedicated broadcast subject
(fabric.capabilities.discover) that all NCS instances subscribe to,
enabling proper scatter-gather discovery across nodes.

Made-with: Cursor

services/memory-service/Dockerfile

@@ -3,6 +3,10 @@ FROM python:3.11-slim
 
 WORKDIR /app
 
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    espeak-ng \
+    && rm -rf /var/lib/apt/lists/*
+
 # Install dependencies
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
@@ -16,7 +20,7 @@ ENV PYTHONUNBUFFERED=1
 
 # Health check
 HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
-    CMD curl -f http://localhost:8000/health || exit 1
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health', timeout=3)" || exit 1
 
 # Run
 EXPOSE 8000