refactor: update regen prefix to be dereferencable and on a subdomain

[wgwz]

Description

Closes: #39

NOTE: To review, only look at this commit. The other commits are from these PR's which will be merged soon:

• https://github.com/regen-network/regen-registry-standards/pull/40
• https://github.com/regen-network/regen-registry-standards/pull/42

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