v0.15.7: Fix backup page storage display & rename system drive label

- Add StorageBars to backupsHandler so all registered storage paths appear
- Update backups.html to use StorageBars loop (replacing single HDDConfigured block)
- Rename "SSD (/)" → "Rendszer (/)" on backup, monitoring, and dashboard pages

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

controller/internal/web/handlers.go

@@ -434,6 +434,7 @@ func (s *Server) backupsHandler(w http.ResponseWriter, r *http.Request) {
 
 	// System info for storage overview bars
 	data["SystemInfo"] = system.GetInfo(s.primaryHDDPath(), s.cpuCollector)
+	data["StorageBars"] = s.buildStorageBars()
 
 	if s.backupMgr != nil {
 		nextDBDump := scheduler.NextDailyRun(s.cfg.Backup.DBDumpSchedule)