v0.25.0 — Debug page: operator testing & diagnostics dashboard

Debug-mode-only dashboard (/debug) with 8 collapsible sections:
system diagnostics, notification testing, backup triggers, storage
simulation, hub & connectivity, self-update dry-run, DR/setup wizard,
and in-memory log viewer. Migrates debug dump from API router to web
server. Adds ring buffer log capture, storage disconnect simulation,
event history tracking, and cross-drive/self-update test methods.

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

controller/internal/selfupdate/updater.go

@@ -234,6 +234,67 @@ func imageName(image string) string {
 	return parts[len(parts)-1]
 }
 
+// DryRunResult holds the result of a self-update dry run.
+type DryRunResult struct {
+	CurrentVersion  string `json:"current_version"`
+	LatestVersion   string `json:"latest_version"`
+	UpdateAvailable bool   `json:"update_available"`
+	ComposeWritable bool   `json:"compose_writable"`
+	CurrentImageLine string `json:"current_image_line"`
+	NewImageLine     string `json:"new_image_line"`
+	BackupRunning   bool   `json:"backup_running"`
+	Error           string `json:"error,omitempty"`
+}
+
+// DryRun checks for updates and reports what would happen without performing any changes.
+func (u *Updater) DryRun() *DryRunResult {
+	result := &DryRunResult{
+		CurrentVersion: u.currentVer,
+	}
+
+	// Check for update
+	check := u.CheckForUpdate()
+	result.LatestVersion = check.LatestVersion
+	result.UpdateAvailable = check.UpdateAvailable
+	if check.Error != "" {
+		result.Error = check.Error
+		return result
+	}
+
+	// Check compose file
+	data, err := os.ReadFile(u.composePath)
+	if err != nil {
+		result.Error = fmt.Sprintf("Compose fájl nem olvasható: %v", err)
+		return result
+	}
+
+	// Find current image line
+	re := regexp.MustCompile(`(image:\s*)gitea\.dooplex\.hu/admin/felhom-controller:\S+`)
+	match := re.Find(data)
+	if match != nil {
+		result.CurrentImageLine = string(match)
+	}
+
+	// Build new image line
+	if check.UpdateAvailable {
+		result.NewImageLine = fmt.Sprintf("image: %s:%s", u.cfg.Image, check.LatestVersion)
+	}
+
+	// Check writability
+	f, err := os.OpenFile(u.composePath, os.O_WRONLY, 0)
+	if err == nil {
+		f.Close()
+		result.ComposeWritable = true
+	}
+
+	// Check backup running
+	if u.backupRunning != nil {
+		result.BackupRunning = u.backupRunning()
+	}
+
+	return result
+}
+
 // TriggerUpdate starts the self-update process. Returns error immediately if
 // preconditions fail. The actual update runs in a goroutine.
 func (u *Updater) TriggerUpdate(initiatedBy string) error {