Stable IDs & lookup by id

Added

• /api/id/{id} — every available view of a configuration in one call, each entry with its signed image_url. All image options apply.
• /api/id/{id}/{view} — the single-view image endpoint, addressed by id instead of names; identical options and behavior.

Improved

• Configuration ids are now permanent: they survive catalog updates, renames and re-imports. Safe to store and embed.