feat: update language support and enhance API functionality

- Changed the default language in `index.html` from Russian to English, updating the title and button aria-labels for improved accessibility.
- Refactored the `buildFetchOptions` function in `api.js` to include an optional external abort signal, enhancing request management.
- Updated `fetchDuties` and `fetchCalendarEvents` to support request cancellation using the new abort signal, improving error handling.
- Added unit tests for the API functions to ensure proper functionality, including handling of 403 errors and request cancellations.
- Enhanced CSS styles for duty markers to improve visual consistency.
- Removed unused code and improved the overall structure of the JavaScript files for better maintainability.

webapp/js/auth.test.js

@@ -0,0 +1,100 @@
+/**
+ * Unit tests for auth: getTgWebAppDataFromHash, getInitData, isLocalhost.
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import {
+  getTgWebAppDataFromHash,
+  getInitData,
+  isLocalhost,
+} from "./auth.js";
+
+describe("getTgWebAppDataFromHash", () => {
+  it("returns empty string when tgWebAppData= not present", () => {
+    expect(getTgWebAppDataFromHash("foo=bar")).toBe("");
+  });
+
+  it("returns value from tgWebAppData= to next &tgWebApp or end", () => {
+    expect(getTgWebAppDataFromHash("tgWebAppData=encoded%3Ddata")).toBe(
+      "encoded=data"
+    );
+  });
+
+  it("stops at &tgWebApp", () => {
+    const hash = "tgWebAppData=value&tgWebAppVersion=6";
+    expect(getTgWebAppDataFromHash(hash)).toBe("value");
+  });
+
+  it("decodes URI component", () => {
+    expect(getTgWebAppDataFromHash("tgWebAppData=hello%20world")).toBe(
+      "hello world"
+    );
+  });
+});
+
+describe("getInitData", () => {
+  const origLocation = window.location;
+  const origTelegram = window.Telegram;
+
+  afterEach(() => {
+    window.location = origLocation;
+    window.Telegram = origTelegram;
+  });
+
+  it("returns initData from Telegram.WebApp when set", () => {
+    window.Telegram = { WebApp: { initData: "sdk-init-data" } };
+    delete window.location;
+    window.location = { ...origLocation, hash: "", search: "" };
+    expect(getInitData()).toBe("sdk-init-data");
+  });
+
+  it("returns data from hash tgWebAppData when SDK empty", () => {
+    window.Telegram = { WebApp: { initData: "" } };
+    delete window.location;
+    window.location = {
+      ...origLocation,
+      hash: "#tgWebAppData=hash%20data",
+      search: "",
+    };
+    expect(getInitData()).toBe("hash data");
+  });
+
+  it("returns empty string when no source", () => {
+    window.Telegram = { WebApp: { initData: "" } };
+    delete window.location;
+    window.location = { ...origLocation, hash: "", search: "" };
+    expect(getInitData()).toBe("");
+  });
+});
+
+describe("isLocalhost", () => {
+  const origLocation = window.location;
+
+  afterEach(() => {
+    window.location = origLocation;
+  });
+
+  it("returns true for localhost", () => {
+    delete window.location;
+    window.location = { ...origLocation, hostname: "localhost" };
+    expect(isLocalhost()).toBe(true);
+  });
+
+  it("returns true for 127.0.0.1", () => {
+    delete window.location;
+    window.location = { ...origLocation, hostname: "127.0.0.1" };
+    expect(isLocalhost()).toBe(true);
+  });
+
+  it("returns true for empty hostname", () => {
+    delete window.location;
+    window.location = { ...origLocation, hostname: "" };
+    expect(isLocalhost()).toBe(true);
+  });
+
+  it("returns false for other hostnames", () => {
+    delete window.location;
+    window.location = { ...origLocation, hostname: "example.com" };
+    expect(isLocalhost()).toBe(false);
+  });
+});