feat: implement heartbeat and event reporting in node daemon

Author: richiemcilroy

crates/sandchest-node/build.rs

@@ -1,8 +1,8 @@
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    // Node proto — server stubs (control plane connects to us)
+    // Node proto — server stubs for Node service, client stubs for Control service
     tonic_build::configure()
         .build_server(true)
-        .build_client(false)
+        .build_client(true)
         .compile_protos(
             &["sandchest/node/v1/node.proto"],
             &["../../packages/contract/proto"],

crates/sandchest-node/src/config.rs

@@ -147,6 +147,7 @@ pub struct NodeConfig {
     pub grpc_port: u16,
     pub data_dir: String,
     pub kernel_path: String,
+    pub control_plane_url: Option<String>,
 }
 
 impl NodeConfig {
@@ -162,6 +163,7 @@ impl NodeConfig {
                 .unwrap_or_else(|_| "/var/sandchest".to_string()),
             kernel_path: std::env::var("SANDCHEST_KERNEL_PATH")
                 .unwrap_or_else(|_| "/var/sandchest/images/vmlinux-5.10".to_string()),
+            control_plane_url: std::env::var("SANDCHEST_CONTROL_PLANE_URL").ok(),
         }
     }