feat: expand Docker build to all features, add docker-compose.yml

- Build with server, mcp, swagger, client, tls features (all except magic)
- Add KEEP_* environment variable documentation and defaults
- Copy CA certificates for HTTPS client support in scratch image
- Add docker-compose.yml with keep-data and keep-config volumes

docker-compose.yml

@@ -0,0 +1,27 @@
+services:
+  keep:
+    build: .
+    ports:
+      - "21080:21080"
+    volumes:
+      - keep-data:/data
+      - keep-config:/config
+    environment:
+      - KEEP_SERVER_ADDRESS=0.0.0.0
+      - KEEP_SERVER_PORT=21080
+      # - KEEP_SERVER_PASSWORD=changeme
+      # - KEEP_SERVER_PASSWORD_HASH=
+      # - KEEP_COMPRESSION=lz4
+      # - KEEP_META_PLUGINS=
+      # - KEEP_FILTERS=
+      - KEEP_CONFIG=/config/config.yml
+      # - KEEP_SERVER_CERT=/certs/cert.pem
+      # - KEEP_SERVER_KEY=/certs/key.pem
+    restart: unless-stopped
+    # For TLS, mount certificate files:
+    # volumes:
+    #   - ./certs:/certs:ro
+
+volumes:
+  keep-data:
+  keep-config: