feat(FN-3109): add Docker connectivity service and target selector UI

This merge adds Docker connectivity management to Fusion (FN-3109), introducing a Docker client service in `@fusion/core` with typed interfaces for daemon connection configuration (host, socket path, TLS). The dashboard gains a `DockerTargetSelector` component for choosing between local socket and T

Fusion-Task-Id: FN-3109

packages/dashboard/app/components/__tests__/DockerTargetSelector.test.tsx

@@ -0,0 +1,40 @@
+import { fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import { DockerTargetSelector } from "../DockerTargetSelector";
+
+vi.mock("lucide-react", () => ({ RefreshCw: () => null }));
+
+const hookState = {
+  contexts: [{ name: "default", isCurrentContext: true }],
+  isLoadingContexts: false,
+  contextsError: null,
+  loadContexts: vi.fn().mockResolvedValue(undefined),
+  testConnection: vi.fn().mockResolvedValue({ success: true, dockerVersion: "24.0" }),
+  isTestingConnection: false,
+  lastTestResult: null,
+  checkLocalDocker: vi.fn().mockResolvedValue({ available: true, version: "24.0" }),
+  isCheckingLocal: false,
+};
+
+vi.mock("../../hooks/useDockerTargets", () => ({ useDockerTargets: () => hookState }));
+
+describe("DockerTargetSelector", () => {
+  it("renders modes and emits config", async () => {
+    const onChange = vi.fn();
+    render(<DockerTargetSelector onChange={onChange} />);
+
+    expect(screen.getByText("Local Docker")).toBeInTheDocument();
+    expect(screen.getByText("Docker Context")).toBeInTheDocument();
+    expect(screen.getByText("Remote Host")).toBeInTheDocument();
+
+    fireEvent.click(screen.getByText("Docker Context"));
+    await waitFor(() => expect(hookState.loadContexts).toHaveBeenCalled());
+
+    fireEvent.click(screen.getByText("Remote Host"));
+    expect(screen.getByPlaceholderText("tcp://host:2376")).toBeInTheDocument();
+
+    fireEvent.click(screen.getByText("Test Connection"));
+    await waitFor(() => expect(hookState.testConnection).toHaveBeenCalled());
+    expect(onChange).toHaveBeenCalled();
+  });
+});