feat: [UIE-10309] - IAM: last login text for delegates

[aaleksee-akamai]

Description 📝

This PR updates a last login field for the delegate users to show 'Not applicable' instead of 'Never'

Changes 🔄

List any change(s) relevant to the reviewer.

• Update logic
• Update text

Scope 🚢

Upon production release, changes in this PR will be visible to:

• All customers
• Some customers (e.g. in Beta or Limited Availability)
• No customers / Not applicable

Preview 📷

Before	After

How to test 🧪

Prerequisites

(How to setup test environment)

• use parent account

Reproduction steps

(How to reproduce the issue, if applicable)

• login as a parent
• switch account
• go to /iam/users

Verification steps

(How to verify changes)

• Last login field for the delegate users should show 'Not applicable'

Author Checklists

As an Author, to speed up the review process, I considered 🤔

👀 Doing a self review
❔ Our contribution guidelines
🤏 Splitting feature into small PRs
➕ Adding a changeset
🧪 Providing/improving test coverage
🔐 Removing all sensitive information from the code and PR description
🚩 Using a feature flag to protect the release
👣 Providing comprehensive reproduction steps
📑 Providing or updating our documentation
🕛 Scheduling a pair reviewing session
📱 Providing mobile support
♿ Providing accessibility support

• I have read and considered all applicable items listed above.

As an Author, before moving this PR from Draft to Open, I confirmed ✅

• All tests and CI checks are passing
• TypeScript compilation succeeded without errors
• Code passes all linting rules

[mpolotsk-akamai]

Looks good! Thanks!