v0.4.5: Add dedicated Backup page (Biztonsági mentés)

New /backups page with full backup system visibility:
- Status overview cards (local/remote backup, DB count, repo size)
- Schedule section with next-run times and retention policy
- Database table with type, size, validation (table count), status
- Snapshot history table with per-snapshot stats
- Repository info card with paths, integrity status, remote placeholder
- "Mentés most" button with auto-refresh polling
- Empty state when backup not configured

Backend: SnapshotRecord history (ring buffer), DumpValidation,
ListDumpFiles, ListSnapshots, GetFullStatus, restic check tracking.
Server accepts scheduler for next-run time calculation.

Sidebar nav updated with 3rd item, dashboard backup card title clickable.

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

controller/internal/web/server.go

@@ -12,6 +12,7 @@ import (
 
 	"gitea.dooplex.hu/admin/felhom-controller/internal/backup"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/config"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/scheduler"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
 	"gitea.dooplex.hu/admin/felhom-controller/internal/system"
 )
@@ -21,6 +22,7 @@ type Server struct {
 	stackMgr     *stacks.Manager
 	cpuCollector *system.CPUCollector
 	backupMgr    *backup.Manager
+	scheduler    *scheduler.Scheduler
 	logger       *log.Logger
 	version      string
 	tmpl         *template.Template
@@ -29,12 +31,13 @@ type Server struct {
 	sessionsMu sync.RWMutex
 }
 
-func NewServer(cfg *config.Config, stackMgr *stacks.Manager, cpuCollector *system.CPUCollector, backupMgr *backup.Manager, logger *log.Logger, version string) *Server {
+func NewServer(cfg *config.Config, stackMgr *stacks.Manager, cpuCollector *system.CPUCollector, backupMgr *backup.Manager, sched *scheduler.Scheduler, logger *log.Logger, version string) *Server {
 	s := &Server{
 		cfg:          cfg,
 		stackMgr:     stackMgr,
 		cpuCollector: cpuCollector,
 		backupMgr:    backupMgr,
+		scheduler:    sched,
 		logger:       logger,
 		version:      version,
 		sessions:     make(map[string]*session),
@@ -59,6 +62,8 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		s.dashboardHandler(w, r)
 	case path == "/stacks":
 		s.stacksHandler(w, r)
+	case path == "/backups":
+		s.backupsHandler(w, r)
 	case strings.HasPrefix(path, "/stacks/") && strings.HasSuffix(path, "/logs"):
 		name := strings.TrimPrefix(path, "/stacks/")
 		name = strings.TrimSuffix(name, "/logs")