feat: add MCP server with resources, tools, auth, and Traefik routing

- Add backend/app/mcp_server.py with FastMCP server (hms-cms)
- Resources: design-rules, page-structure, sync-status
- Tools: trigger_sync, get_sync_log, set_rentman_token, read_file,
  write_file, create_page, deploy, git_commit, git_status
- Bearer token auth via MCP_AUTH_TOKEN env var
- Mount MCP at /mcp with streamable HTTP transport
- Integrate session manager in FastAPI lifespan
- Add Traefik labels for external /mcp route on hms.media-on.de
- Add git, docker.io, curl to backend Dockerfile
- Mount repo root + docker socket in backend container
- Add mcp>=1.0.0 to requirements.txt

frontend-nuxt-old/tests/e2e/error-pages.spec.ts

@@ -0,0 +1,10 @@
+import { test, expect } from "@playwright/test";
+
+test.describe("Error Pages", () => {
+  test("404 page should show 'Seite nicht gefunden'", async ({ page }) => {
+    const response = await page.goto("/nicht-existent");
+    expect(response?.status()).toBe(404);
+    await expect(page.locator("body")).toContainText("Seite nicht gefunden");
+    await expect(page.getByRole("link", { name: /Startseite/ })).toBeVisible();
+  });
+});