allow sending reports to external users with magic tokens

[pjain1]

Fixes https://github.com/rilldata/rill/issues/5273

• UI changes needs to be done to handle the new external urls for opening and exporting report containing magic token as path param. Urls for existing users will work as it is.

Clean up of unused magic tokens for reports directly created in code (not through UI) needs to be done. Its a bit tricky, may be some background job is required that queries report_tokens table and for each report_name queries the runtime and then does clean up.