Improve SALT licensing documentation with additional technical details

[jdiehl]

This update expands the SALT licensing page with information gaps identified through internal Q&A review.

Changes:

• Version compatibility: Clarified that a SALT license permits use of the purchased major version and all prior major versions. Added guidance on upgrading to a newer major version via a maintenance contract.
• License scope: Added a note that a single license file covers all Mendix applications; multiple files cannot be issued.
• User limits: Added a new Limitations subsection documenting that licenses enforce a named user maximum, defined at purchase, per application. Concurrent user limiting is not supported.
• On-premises hardware ID: Added an info alert explaining that on-premises deployments require generating a hardware ID (CID) using Siemens tools before license provisioning.
• Offline operation: Added a FAQ confirming that SALT-based licenses operate fully offline with no outbound connectivity to Siemens required.
• Trial mode: Clarified what trial mode means in practice (limited users and runtime) when the license server is unavailable at startup.
• Minor fixes: Fixed typo in front matter description ("Advaned" → "Advanced") and a truncated sentence in the FAQs ("license serve" → "license server").

[jdiehl]

@emirmx Could you review these changes please?

[emirmx]

I assume you explicitly did not mention internal/external user distinction.