Implement kaya-rbcs: simplified RBCS clone on the Kaya framework

- KayaApp with GET/PUT recursive routes backed by memcached (aiomcache)
- env-based configuration, metadata-aware value encoding, key prefix/digest
- Granian RSGI launcher (rbcs-server / python -m kaya_rbcs)
- pinned requirements via pip-compile, alpine:3.24 Dockerfile with healthcheck
- offline tests using an in-process fake memcached
- Gitea Actions workflow to build and push the multi-arch Docker image

Dockerfile

@@ -0,0 +1,37 @@
+FROM alpine:3.24
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1 \
+    PIP_NO_CACHE_DIR=1 \
+    RBCS_HOST=0.0.0.0 \
+    RBCS_PORT=8080 \
+    RBCS_MEMCACHE_HOST=memcached \
+    RBCS_MEMCACHE_PORT=11211
+
+RUN apk add --no-cache python3
+
+WORKDIR /opt/kaya-rbcs
+
+COPY requirements.txt ./
+RUN python3 -m venv /opt/venv \
+    && /opt/venv/bin/pip install -r requirements.txt
+
+COPY pyproject.toml README.md ./
+COPY src ./src
+RUN /opt/venv/bin/pip install --no-deps .
+
+RUN addgroup -S rbcs \
+    && adduser -S -G rbcs rbcs \
+    && chown -R rbcs:rbcs /opt/kaya-rbcs /opt/venv
+
+ENV PATH="/opt/venv/bin:${PATH}"
+
+USER rbcs
+
+EXPOSE 8080
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+    CMD python3 -c "import socket, os; socket.create_connection(('127.0.0.1', int(os.environ['RBCS_PORT'])), timeout=3).close()"
+
+ENTRYPOINT ["rbcs-server"]