For Training

This PR has very little to teach end users — the training need here is almost entirely for internal Dentolize staff (support, and admins using the internal dashboard). For clinic users, the only new thing worth a one-line mention is the account switcher.

Teaching clinic users: the account switcher (2 minutes)

1. Open the profile menu (top-right user icon).
2. Point out the new Add Account option.
3. Click it, show the two tabs — By Email and By Username (clinic login name + username) — and explain you can add any account you have access to, in any region, without losing your current session.
4. After adding a second account, reopen the profile menu and show the avatar list — click between accounts to demonstrate the instant switch.
5. Mention: removing an account from this list just forgets it locally; it doesn't delete or disable the account itself.

That's the entire end-user training surface. Everything else in this PR is invisible to clinic staff by design.

Teaching internal admins: the regional Cron Jobs screen (5 minutes)

1. Navigate to the admin dashboard's Cron Jobs screen.
2. Point out the new Region dropdown at the top — explain that cron job status, the "Execute" buttons, and the Redis key tools all scope to whichever region is selected, because each region now runs its own independent cron/queue workers and its own Redis instance.
3. Walk through checking a job's status, executing a job, and reading/resetting a Redis key — same as before, just region-scoped now.
4. Note that the Companies list and most other admin screens are unchanged and still show data merged across every region automatically — the region selector only appears where an action is inherently region-specific (cron, Redis).

Teaching operators: company-region migration (advanced, ops-only)

This is not end-user or admin-dashboard training — it's a CLI tool for whoever runs production migrations. Do not train broad admin staff on this; it's destructive if misused. If a migration runbook walkthrough is needed, base it directly on packages/auth-server/src/scripts/companyRegionMigration/README.md and require a dry run be demonstrated before any real-migration demonstration. See Moving a Company Between Regions for the concept-level summary.