feat: support Docker volume-based JAR mounting for Docker-in-Docker

When CAMELEER_JAR_DOCKER_VOLUME is set, the orchestrator mounts the
named volume at the jar storage path instead of using a host bind mount.
This solves the path translation issue in Docker-in-Docker setups where
the server runs inside a container and manages sibling containers.

The entrypoint is overridden to use the volume-mounted JAR path via
the CAMELEER_APP_JAR env var.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-core/src/main/java/com/cameleer3/server/core/runtime/ContainerRequest.java

@@ -7,6 +7,8 @@ public record ContainerRequest(
         String containerName,
         String baseImage,
         String jarPath,
+        String jarVolumeName,
+        String jarVolumeMountPath,
         String network,
         List<String> additionalNetworks,
         Map<String, String> envVars,