Port main-menu JS files to TypeScript

- Port all 4 files in src/app/layouts/default/header/menus/main-menu to .tsx
- Add type annotations following guidelines: avoid any, prefer type over interface
- Use inline type definitions for function parameters
- Rely on type inference where possible
- Keep line lengths under 120 characters

Related to CORE-1266

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Fix lint issues

Fix window.SETTINGS type assertion

Use double type assertion via unknown to properly convert Window type.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Fix TypeScript type issues in main-menu files

- Make children props optional to handle JSX children
- Add type assertion for window.SETTINGS
- Add explicit types for filter/map callbacks
- Use index as fallback key in map operations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: 2 people

src/app/layouts/default/header/menus/main-menu/login-menu/login-menu-with-dropdown.tsx

@@ -3,8 +3,10 @@ import {useLocation} from 'react-router-dom';
 import useUserContext from '~/contexts/user';
 import linkHelper from '~/helpers/link';
 import Dropdown, {MenuItem} from '../dropdown/dropdown';
+import type {WindowWithSettings} from '~/helpers/window-settings';
+import {assertDefined} from '~/helpers/data';
 
-const settings = (window as unknown as {SETTINGS: {accountHref: string}}).SETTINGS;
+const settings = (window as WindowWithSettings).SETTINGS;
 const reqFacultyAccessLink = `${settings.accountHref}/i/signup/educator/cs_form`;
 const profileLink = `${settings.accountHref}/profile`;
 
@@ -21,7 +23,7 @@ function AccountItem() {
 
 
 export default function LoginMenuWithDropdown() {
-    const {userModel} = useUserContext();
+    const userModel = assertDefined(useUserContext().userModel);
 
     // updates logoutLink
     useLocation();

src/app/layouts/default/header/menus/main-menu/main-menu.tsx

@@ -111,6 +111,7 @@ function SubjectsMenu() {
     );
 }
 
+// eslint-disable-next-line complexity
 function navigateWithArrows(event: React.KeyboardEvent<HTMLUListElement>) {
     switch (event.key) {
         case 'ArrowRight':