feat: infra backup GFS retention + version history

New infra_backup_versions table with GFS pruning (~14 versions per
customer). Recovery endpoint supports ?version=ID. New /versions API.
Dashboard shows collapsible backup history with app names and disk count.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hub/internal/web/configs.go

@@ -231,6 +231,7 @@ func (s *Server) handleCustomerUnified(w http.ResponseWriter, r *http.Request, c
 	var recentNotifs []store.NotificationLogEntry
 	var infraMeta *store.InfraBackupMeta
 	var infraBackupAge string
+	var infraBackupVersions []store.InfraBackupVersion
 	var events []store.Event
 	var eventCounts map[string]int
 
@@ -244,6 +245,7 @@ func (s *Server) handleCustomerUnified(w http.ResponseWriter, r *http.Request, c
 		if infraMeta != nil {
 			infraBackupAge = timeAgo(infraMeta.UpdatedAt)
 		}
+		infraBackupVersions, _ = s.store.ListInfraBackupVersions(customerID)
 		events, _ = s.store.GetRecentEvents(customerID, 50)
 		eventCounts, _ = s.store.CountEventsBySeverity(customerID, time.Now().Add(-24*time.Hour))
 		appTelemetry, _ = s.store.GetCustomerAppSummary(customerID, time.Now().Add(-7*24*time.Hour))
@@ -274,6 +276,7 @@ func (s *Server) handleCustomerUnified(w http.ResponseWriter, r *http.Request, c
 
 		InfraBackup         *store.InfraBackupMeta
 		InfraBackupAge      string
+		InfraBackupVersions []store.InfraBackupVersion
 		NotifPrefs          *store.NotificationPrefs
 		RecentNotifications []store.NotificationLogEntry
 		History             []store.CustomerSummary
@@ -315,6 +318,7 @@ func (s *Server) handleCustomerUnified(w http.ResponseWriter, r *http.Request, c
 
 		InfraBackup:         infraMeta,
 		InfraBackupAge:      infraBackupAge,
+		InfraBackupVersions: infraBackupVersions,
 		NotifPrefs:          notifPrefs,
 		RecentNotifications: recentNotifs,
 		History:             history,