Make sure the Menas uses only one source of project version information

## Background
Project version used in Spring (Menas UI) in different parts of code can theoretically diverge, which would break the UI

## Feature
`"/${enceladusVersion()}/**"` is supposed to be a root path to our sources. Which is set using `spring.resources.chain.strategy.fixed.version` from app properties. But here we "enable" it using `ProjectMetadata.enceladusVersion`. And in some other places of our project (`index.html`), we again use `ProjectMetadata.enceladusVersion`. If these two versions ever become different, Menas becomes unusable.

Trace the uses of ProjectMetadata.enceladusVersion, enceladusVersion(), spring.resources.chain.strategy.fixed.version, and the version reference in index.html. Determine where the project version is defined and how the Spring resource path and Menas UI consume it. Done means these consumers use one consistent source so the UI cannot break when versions diverge.

索引モデルが issue の本文から書いたものです。