Add missing Zendesk users to Simplesat without duplicates

**Objective:** Find Zendesk end users (optionally only in organization `{organization-name}`) who have no Simplesat customer record, and create them in Simplesat only after the user confirms.

**Step 1: Zendesk end users**

Call `zendesk-get-user` with `role` = end-user and `active` = true. If `{organization-name}` is given, also pass it as `organization-name`. Drop users with no `email`. Stop after 100 users and say the list was capped.

**Step 2: Check Simplesat**

For each user, call `simplesat-get-customer` with `email` = the user's `email`. Compare case-insensitively. If no match, call `simplesat-get-customer` with `external-id` = the Zendesk `user-id` in case the email changed. Keep only users with no match either way.

**Step 3: Report and ask**

List each missing user: Zendesk user id, name, email, organization. Then ask: "Create these N customers in Simplesat?" Do not continue without a yes.

**Step 4: Create (only after yes)**

For each confirmed user, call `simplesat-add-customer` once with `email` = the user's email, `name` = their name, `company` = their `organization-name`, and `external-id` = their Zendesk `user-id`. Then call `simplesat-get-customer` with that `email` to confirm the record exists.

**Rules & Guidelines:**

* `zendesk-get-user` is on the zendesk server. `simplesat-get-customer` and `simplesat-add-customer` are on the simplesat server.
* The only write is `simplesat-add-customer`. Never write to Zendesk: do NOT call `zendesk-add-user` or `zendesk-update-user`.
* Do NOT create a customer whose email already exists in Simplesat under different capitalisation.

**Validation:**

* If every user already exists in Simplesat, say so and stop without writing.
* If a Simplesat customer matches by email but has a different name or company, report it as a mismatch and do not change it.
* If a create fails, report the email and the error, and carry on with the rest.