Fixes #39394 - Handle empty taxonomy scopes in authorizer

[jakduch]

Summary

Non-admin users with only an organization or only a location assigned could receive a 500 response when listing taxable resources.

An empty taxonomy intersection was represented as a contradictory Scoped Search expression using set? and null?. Unlike regular has-many conditions, Scoped Search does not wrap these operators in a subquery, leaving a direct reference to the taxonomies table after the eager-loads were removed in #39209.

Represent empty taxonomy intersections as no access and let the authorizer add an explicit false SQL condition. Filters without an overlapping taxonomy are skipped individually in the non-granular path.

This preserves the duplicate-result fix from #39209 without restoring the removed taxonomy eager-loads.

Testing

• Ruby syntax checks pass for all changed files
• Foreman RuboCop passes for all changed files
• Regression tests cover users without organizations and users without locations

AI usage disclosure

Per the community discussion on AI policy, the issue was investigated and the changes, tests, and PR wording were prepared with the assistance of Codex 5.6 Sol High. The resulting changes were reviewed before submitting. The commit also includes an Assisted-By trailer.