feat: DockerNetworkManager with lazy network creation and container attachment

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/runtime/DockerNetworkManager.java

@@ -0,0 +1,62 @@
+package com.cameleer3.server.app.runtime;
+
+import com.github.dockerjava.api.DockerClient;
+import com.github.dockerjava.api.model.Network;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+public class DockerNetworkManager {
+
+    private static final Logger log = LoggerFactory.getLogger(DockerNetworkManager.class);
+    public static final String TRAEFIK_NETWORK = "cameleer-traefik";
+    public static final String ENV_NETWORK_PREFIX = "cameleer-env-";
+
+    private final DockerClient dockerClient;
+
+    public DockerNetworkManager(DockerClient dockerClient) {
+        this.dockerClient = dockerClient;
+    }
+
+    public String ensureNetwork(String networkName) {
+        List<Network> existing = dockerClient.listNetworksCmd()
+                .withNameFilter(networkName)
+                .exec();
+
+        for (Network net : existing) {
+            if (net.getName().equals(networkName)) {
+                return net.getId();
+            }
+        }
+
+        String id = dockerClient.createNetworkCmd()
+                .withName(networkName)
+                .withDriver("bridge")
+                .withCheckDuplicate(true)
+                .exec()
+                .getId();
+
+        log.info("Created Docker network: {} ({})", networkName, id);
+        return id;
+    }
+
+    public void connectContainer(String containerId, String networkName) {
+        String networkId = ensureNetwork(networkName);
+        try {
+            dockerClient.connectToNetworkCmd()
+                    .withContainerId(containerId)
+                    .withNetworkId(networkId)
+                    .exec();
+            log.debug("Connected container {} to network {}", containerId, networkName);
+        } catch (Exception e) {
+            if (!e.getMessage().contains("already exists")) {
+                throw e;
+            }
+        }
+    }
+
+    public static String envNetworkName(String envSlug) {
+        return ENV_NETWORK_PREFIX + envSlug;
+    }
+}

cameleer3-server-app/src/main/java/com/cameleer3/server/app/runtime/RuntimeOrchestratorAutoConfig.java

@@ -25,4 +25,12 @@ public class RuntimeOrchestratorAutoConfig {
         log.info("No Docker socket or K8s detected - runtime management disabled (observability-only mode)");
         return new DisabledRuntimeOrchestrator();
     }
+
+    @Bean
+    public DockerNetworkManager dockerNetworkManager(RuntimeOrchestrator orchestrator) {
+        if (orchestrator instanceof DockerRuntimeOrchestrator docker) {
+            return new DockerNetworkManager(docker.getDockerClient());
+        }
+        return null;
+    }
 }