fix: remove obsolete /data/documents and /config dirs from Dockerfiles

doc-service and ai-service no longer use local filesystem directories —
all file and config I/O goes through storage-service. Update README and
CLAUDE.md to reflect 6-service architecture, new volumes, and add
storage-service step to the "Adding a new resource" checklist.

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

features/ai-service/Dockerfile

@@ -15,8 +15,7 @@ FROM python:3.12-slim
 RUN groupadd --gid 1001 appuser && \
     useradd --uid 1001 --gid 1001 --no-create-home --shell /bin/sh appuser
 
-# Pre-create the config directory with correct ownership
-RUN mkdir -p /config && chown -R appuser:appuser /config
+# No filesystem directories needed — all config goes through storage-service.
 
 WORKDIR /app