Shares of other services and RepoISO integration

- include SMB drop-ins from /etc/samba/smb.conf.d into the generated smb.conf
- keep smbd/nfs-server running while other services (/etc/exports.d, drop-ins) share,
  instead of disabling them when nasmon has no shares of its own
- list those shares read-only on /shares
- settings: RepoISO URL; poll its /api/integration/status, dashboard card, menu link,
  alerts for portal down, stale worker, failed jobs, unmounted publications

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/config/config.go

@@ -40,15 +40,23 @@ type SelfTests struct {
 	Hour      int  `json:"hour"` // local hour of day when tests may be started
 }
 
+// Integrations links nasmon with other services on the same host.
+type Integrations struct {
+	// RepoISOURL is the RepoISO portal base URL nasmon polls for health
+	// (e.g. http://127.0.0.1); empty disables the integration.
+	RepoISOURL string `json:"repoiso_url"`
+}
+
 type Settings struct {
-	SMTP             SMTP       `json:"smtp"`
-	AlertsEnabled    bool       `json:"alerts_enabled"`
-	NotifyResolved   bool       `json:"notify_resolved"`
-	RemindHours      int        `json:"remind_hours"`
-	SmartIntervalMin int        `json:"smart_interval_min"`
-	SmartSkipStandby bool       `json:"smart_skip_standby"`
-	Thresholds       Thresholds `json:"thresholds"`
-	SelfTests        SelfTests  `json:"self_tests"`
+	SMTP             SMTP         `json:"smtp"`
+	AlertsEnabled    bool         `json:"alerts_enabled"`
+	NotifyResolved   bool         `json:"notify_resolved"`
+	RemindHours      int          `json:"remind_hours"`
+	SmartIntervalMin int          `json:"smart_interval_min"`
+	SmartSkipStandby bool         `json:"smart_skip_standby"`
+	Thresholds       Thresholds   `json:"thresholds"`
+	SelfTests        SelfTests    `json:"self_tests"`
+	Integrations     Integrations `json:"integrations"`
 }
 
 func Defaults() Settings {
@@ -102,6 +110,11 @@ func (s *Settings) Validate() error {
 	if s.SelfTests.ShortDays < 0 || s.SelfTests.LongDays < 0 {
 		return errors.New("self-test periods must be >= 0")
 	}
+	u := strings.TrimRight(strings.TrimSpace(s.Integrations.RepoISOURL), "/")
+	if u != "" && !strings.HasPrefix(u, "http://") && !strings.HasPrefix(u, "https://") {
+		return errors.New("RepoISO URL must start with http:// or https://")
+	}
+	s.Integrations.RepoISOURL = u
 	return nil
 }