fix: frontend bugs relating to redirects/tenants

[abelanger5]

Fixes the following frontend and onboarding bugs:

• Adds a query param tenant to application routes, with the following behavior:
  • When there is a tenant parameter set which the user is a member of, the application will set that as the currently selected tenant
  • When there is a tenant parameter set which the user is not a member of, or there is not a tenant parameter set, the application will look in localStorage for the value of lastTenant and set that as the currently selected tenant
  • When there is not a lastTenant value set, or the user is not a member of that tenant, the application will select the first tenant in the membership list

Additionally, this PR adds the following:

• Allows setting an environment variable SERVER_AUTH_SET_EMAIL_VERIFIED to true which automatically sets the email to verified for new signups, since most local installations won't have an email verification mechanism
• When a user is logged in, navigating to /auth/login or /auth/register will redirect to the application via the no-auth.tsx middleware
• When there are no events found, the backend will no longer respond with a 500-level error, and will return 0 rows instead