Feat auth: allow additional secrets as env variables

fix error when db persistence enabled (#57)

Add support for existing secret references

* Add note to vector volume mount

* exclude empty secret from being encoded

Update images to match official Supabase Docker compose

* add helm install notes
* add environment variable support to vector
* update image tags
* update README on vector volume
* fix vector volume error

* fix storage fails to deploy if minio stub exists
* update postgres-meta image tag