Add Proxmox Backup Server datastore management: overview, datastore detail, download/prune/verify/GC dialogs, usePbs hook, backend commands, and tests.
Fix macOS keychain re-writes failing with 'item already exists': replace keyring 3 with keyring-core plus per-platform stores (macOS Keychain, Windows Credential Manager, Linux keyutils), recover by deleting the stale item and retrying once, and surface actionable messages for locked keychains.
mbatchelder
Matt