Handle frontend base URL dynamically for production deployments

[coopernetes]

Original comment:

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This is a common misconception with Vite environment variables. They are only injected at build time, not at run time. My PR (#1165) attempts to make this properly dynamic at run time. It will need proper testing so I'm gonna just make a note here as a reminder to have an issue for this specifically.

https://github.com/RBC/finos-git-proxy/blob/24b91e46fc6288fcba5e8b948937e96a66857aa5/src/ui/services/apiConfig.ts

https://github.com/RBC/finos-git-proxy/blob/24b91e46fc6288fcba5e8b948937e96a66857aa5/src/ui/services/runtime-config.ts

https://github.com/finos/git-proxy/pull/1165/files#diff-79738685a656fe6b25061bb14181442210b599f746faeaba408a2401de45038a

Originally posted by @coopernetes in #1202 (comment)