feat: Evaluate versioning strategy for npm-based theme distribution

[karlbaumhauer]

User Story

As a Solid Design System maintainer, I want to evaluate whether npm-distributed themes need explicit versioning or another compatibility strategy, so that application teams can reliably use Solid themes across different component versions while keeping each brand appearance visually consistent.

Acceptance Criteria

1. The current and future usage model for themes is analyzed, especially that themes are consumed per brand appearance and should provide a consistent overall visual experience.
2. The dependency between theme changes and component versions is evaluated, including cases where new theme tokens or theme adjustments are only supported by specific component versions.
3. At least the following options are compared: versioned theme packages, unversioned/latest theme packages per brand appearance, and backward-compatible themes.
4. The feasibility of keeping themes backward compatible down to the latest major version of the Solid components is assessed.
5. Risks are documented for visual inconsistencies, breaking changes, token availability, and applications using older component versions.

DoR

• Item has business value
• Item all subtasks have been estimated by the team
• Item is clear and well-defined
• Item dependencies have been identified

DoD

• All subtasks have been closed