[Feature] Multi user setup

[DevDuki]

What problem does this solve?

Allow my partner of having her own account, but hide sonarr, radarr and some other services from her, so she can at least use the Dashboard, Discover and Calendar navigations. That way she can request things herself without accidentally breaking any configurations made in sonarr, radarr, etc.

Describe the solution you'd like

Same as above

Alternatives considered

Right now she only has access to my seerr container, but we both like the way Prismarr looks more.

Additional context

Scope check

• I have read the README and confirmed this fits Prismarr's scope
  (dashboard unifying existing services, not replacing them).
• I am willing to contribute a PR for this feature. (optional, not required)