Show BanGUI app version in sidebar, fix version tooltips

- Inject __APP_VERSION__ at build time via vite.config.ts define (reads
  frontend/package.json#version); declare the global in vite-env.d.ts.
- Render 'BanGUI v{__APP_VERSION__}' in the sidebar footer (MainLayout)
  when expanded; hidden when collapsed.
- Rename fail2ban version tooltip to 'fail2ban daemon version' in
  ServerStatusBar so it is visually distinct from the app version.
- Sync frontend/package.json version (0.9.0 → 0.9.3) to match
  Docker/VERSION; update release.sh to keep them in sync on every bump.
- Add vitest define stub for __APP_VERSION__ so tests compile cleanly.
- Add ServerStatusBar and MainLayout test suites (10 new test cases).

frontend/src/layouts/__tests__/MainLayout.test.tsx

@@ -0,0 +1,78 @@
+/**
+ * Tests for the MainLayout component.
+ *
+ * Covers:
+ * - BanGUI application version displayed in the footer when the sidebar is expanded.
+ * - Version text hidden when the sidebar is collapsed.
+ * - Navigation items rendered correctly.
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { MemoryRouter } from "react-router-dom";
+import { FluentProvider, webLightTheme } from "@fluentui/react-components";
+import { MainLayout } from "../../layouts/MainLayout";
+
+// ---------------------------------------------------------------------------
+// Mocks
+// ---------------------------------------------------------------------------
+
+vi.mock("../../providers/AuthProvider", () => ({
+  useAuth: () => ({ logout: vi.fn() }),
+}));
+
+vi.mock("../../hooks/useServerStatus", () => ({
+  useServerStatus: () => ({
+    status: { online: true, version: "1.0.0", active_jails: 1, total_bans: 0, total_failures: 0 },
+    loading: false,
+    error: null,
+    refresh: vi.fn(),
+  }),
+}));
+
+vi.mock("../../hooks/useBlocklist", () => ({
+  useBlocklistStatus: () => ({ hasErrors: false }),
+}));
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function renderLayout(): void {
+  render(
+    <FluentProvider theme={webLightTheme}>
+      <MemoryRouter initialEntries={["/"]}>
+        <MainLayout />
+      </MemoryRouter>
+    </FluentProvider>,
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+describe("MainLayout", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("renders the navigation sidebar", () => {
+    renderLayout();
+    expect(screen.getByRole("navigation", { name: "Main navigation" })).toBeInTheDocument();
+  });
+
+  it("shows the BanGUI version in the sidebar footer when expanded", () => {
+    renderLayout();
+    // __APP_VERSION__ is stubbed to "0.0.0-test" via vitest.config.ts define.
+    expect(screen.getByText("BanGUI v0.0.0-test")).toBeInTheDocument();
+  });
+
+  it("hides the BanGUI version text when the sidebar is collapsed", async () => {
+    renderLayout();
+    const toggleButton = screen.getByRole("button", { name: /collapse sidebar/i });
+    await userEvent.click(toggleButton);
+    expect(screen.queryByText("BanGUI v0.0.0-test")).not.toBeInTheDocument();
+  });
+});