Unify hosted and remote instance list pages

Hosted and remote instance list pages have grown apart over time. Remote instances got proper backend pagination, filtering, stats widgets, and bulk operations, while hosted instances lagged behind. This epic groups the work to bring them to parity and make sure both sides use consistent patterns going forward.

## Goal

By the end of this, team-level and application-level list pages for both hosted and remote instances should feel like the same product: same filtering patterns, same stats overview, same bulk operation capabilities, all backed by proper server-side pagination.