docs: Update Boundary Enterprise licensing info

[Dan-Heath]

This PR recreates boundary PR #5999 in the web-unified-docs repo. It includes the following updates to the previous PR:

• Updates the description of what happens during a graceful shutdown with an existing description from the controller docs
• Explains how the time of license expiration is determined
• Updates the warning message to be more realistic (🤞 )
• Adds the license parameter to the controller configuration docs

View the updates in the preview deployment:

• Boundary Enterprise licensing
• controller stanza configuration

---

From #5999:

Per SPE-1197, a customer had some questions about what happens when the Boundary Enterprise license expires. These included:

• What happens when the license expires? Is there a grace period?
• Are there any notifications prior to expiration?
• How do you update a license key and is there downtime?
• What is the recommended upgrade path?

These scenarios were documented in the Vault docs, and the customer expected to find the information in the Boundary docs too.

This PR updates the Boundary Enterprise licensing documentation with more information about what happens in the scenarios listed above.

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Vercel Previews Deployed

Name	Status	Preview	Updated (UTC)
Dev Portal	✅ Ready (Inspect)	Visit Preview	Thu Nov 13 19:02:37 UTC 2025
Unified Docs API	✅ Ready (Inspect)	Visit Preview	Thu Nov 13 18:55:26 UTC 2025

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[johanbrandhorst]

Thanks!

[stellarsquall]

this is great! thank you 🙏