feat: add controller self-update mechanism (v0.16.0)

New selfupdate package: version parsing, audit state file, updater with
Gitea registry V2 check, docker pull + compose rewrite + compose up flow.

- API: /api/selfupdate/{status,check,update} with session+bearer auth
- UI: Settings "Verzió és frissítés" card with check/install buttons + JS polling
- Scheduler: periodic check (6h default) + optional daily auto-update
- Notifications: success/failure on post-update startup verification
- Alert: info banner when update available
- docker-compose.yml: add directory bind mount for compose file access

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

controller/internal/config/config.go

@@ -118,6 +118,7 @@ type SelfUpdateConfig struct {
 	CheckInterval        string `yaml:"check_interval"`
 	Image                string `yaml:"image"`
 	AutoUpdate           bool   `yaml:"auto_update"`
+	AutoUpdateTime       string `yaml:"auto_update_time"`
 	HealthTimeoutSeconds int    `yaml:"health_timeout_seconds"`
 }
 
@@ -206,6 +207,8 @@ func applyDefaults(cfg *Config) {
 	di(&cfg.Monitoring.Thresholds.TemperatureWarnCelsius, 75)
 	d(&cfg.Hub.PushInterval, "15m")
 	d(&cfg.SelfUpdate.CheckInterval, "6h")
+	d(&cfg.SelfUpdate.Image, "gitea.dooplex.hu/admin/felhom-controller")
+	d(&cfg.SelfUpdate.AutoUpdateTime, "04:30")
 	di(&cfg.SelfUpdate.HealthTimeoutSeconds, 60)
 	d(&cfg.Logging.Level, "info")
 	di(&cfg.Logging.MaxSizeMB, 10)