e2e: persistence tests, verified against a live server

- campaign name survives a reload (autosave debounce respected)
- export/import round trip: Save downloads dashboard.json with the
  current state, Clear blanks it via the confirm modal, Load restores it
- specs take BASE_URL env override (default stays localhost:3000)
- both new tests and the three smoke tests pass on chromium

end2end/tests/persistence.spec.ts

@@ -0,0 +1,74 @@
+import { test, expect, type Page } from "@playwright/test";
+import * as fs from "node:fs";
+
+
+// Override with BASE_URL (e.g. when the dev server runs on another port).
+const BASE = process.env.BASE_URL ?? "http://localhost:3000";
+
+// Collects browser console errors and page errors for the duration of a test.
+function trackErrors(page: Page): string[] {
+  const errors: string[] = [];
+  page.on("console", (msg) => {
+    if (msg.type() === "error") {
+      errors.push(msg.text());
+    }
+  });
+  page.on("pageerror", (err) => {
+    errors.push(String(err));
+  });
+  return errors;
+}
+
+// Autosave is debounced at 500 ms; give it time before reloading.
+const DEBOUNCE_MS = 700;
+
+test("campaign name survives a reload", async ({ page }) => {
+  const errors = trackErrors(page);
+  await page.goto(`${BASE}/`);
+
+  const name = "Кампания с сохранением";
+  const input = page.locator("#campaign-name");
+  await input.fill(name);
+  await page.waitForTimeout(DEBOUNCE_MS);
+
+  await page.reload();
+  await expect(input).toHaveValue(name);
+
+  expect(errors).toEqual([]);
+});
+
+test("export/import round trip through the file", async ({ page }) => {
+  const errors = trackErrors(page);
+  await page.goto(`${BASE}/`);
+
+  // Save: the header button downloads dashboard.json with the current state.
+  const name = "Кампания экспорта";
+  await page.locator("#campaign-name").fill(name);
+  const [download] = await Promise.all([
+    page.waitForEvent("download"),
+    page.getByRole("button", { name: "Сохранить" }).click(),
+  ]);
+  expect(download.suggestedFilename()).toBe("dashboard.json");
+
+  const filePath = await download.path();
+  expect(filePath).not.toBeNull();
+  const saved = JSON.parse(fs.readFileSync(filePath!, "utf8"));
+  expect(saved.campaign).toBe(name);
+
+  // Clear: confirm the dialog, the dashboard goes blank.
+  await page.getByRole("button", { name: "Очистить" }).click();
+  await page.locator(".modal").waitFor();
+  await page.locator(".modal").getByRole("button", { name: "Очистить" }).click();
+  await expect(page.locator(".modal")).toBeHidden();
+  await expect(page.locator("#campaign-name")).toHaveValue("");
+
+  // Load: pick the file we just saved, the state comes back.
+  const [chooser] = await Promise.all([
+    page.waitForEvent("filechooser"),
+    page.getByRole("button", { name: "Загрузить" }).click(),
+  ]);
+  await chooser.setFiles(filePath!);
+  await expect(page.locator("#campaign-name")).toHaveValue(name);
+
+  expect(errors).toEqual([]);
+});

end2end/tests/smoke.spec.ts

@@ -1,6 +1,7 @@
 import { test, expect, type Page } from "@playwright/test";
 
-const BASE = "http://localhost:3000";
+// Override with BASE_URL (e.g. when the dev server runs on another port).
+const BASE = process.env.BASE_URL ?? "http://localhost:3000";
 
 // Collects browser console errors and page errors for the duration of a test.
 function trackErrors(page: Page): string[] {