Add scale profiles for true, compressed, and poster views

[jokiatgithub]

Context

A solar-system engine cannot use one scale for every use case. True scale, educational scale, and poster composition scale need to be deliberate choices.

Roadmap: https://github.com/jokiatgithub/starwatcher/blob/main/docs/solar-system-engine-roadmap.md

Scope

• Add a scale-profile module for true distance, compressed orbit, and poster composition.
• Keep body radius scaling separate from orbital distance scaling.
• Expose scale metadata in scene snapshots.

Acceptance Criteria

• Each scale profile has a clear name and documented behavior.
• Current heliocentric rendering can use the compressed/poster-style profile.
• True scale remains available as a data mode even if it is visually difficult.
• Unit tests cover the transform behavior.