Backups: redesigned detail page

Each backup now has a structured detail page: general info, source VM or disk, storage and savings, recovery objectives (RPO measured as the real age of the copy, RTO as a clearly labelled estimate), encryption and format, and an integrity panel with both SHA-256 checksums you can copy. The backup list also gained filters and sorting inside the table, plus a destination chip showing which backend and country each archive lives in.