fix(dns): retry configurable resolvers

Treat resolver transport failures as inconclusive checks so they do not open outage alerts.

app/models/monitor.go

@@ -297,7 +297,8 @@ var mutex sync.Mutex
 
 // checkSeverityRank assigns an ordinal to each check state so the monitor
 // aggregator can pick the highest-severity child deterministically.
-// Severity order is FAIL > ERR > DEGRADED > WARN > OK — see docs/todo.md
+// Severity order is FAIL > ERR > DEGRADED > WARN > OK. FAIL means the
+// worker could not run a check; it remains visible but never opens alerts.
 // Phase 3 for the rationale (DEGRADED = partial regional failure, sits
 // between OK and ERR). Unknown states (UNK, empty, ...) rank 0 so any
 // real check state takes precedence over them.
@@ -341,7 +342,7 @@ func (m *Monitor) UpdateStatusFromChecks() {
 	// inlined three if-statements with non-obvious precedence (a WARN that
 	// appeared AFTER an ERR in the iteration would never downgrade back,
 	// but a FAIL after ERR would silently get clobbered). Using a single
-	// severity rank keeps the rule FAIL > ERR > DEGRADED > WARN > OK
+	// severity rank keeps the overall health state deterministic.
 	// independent of slice ordering — the same rule Phase 3 introduces
 	// for DEGRADED, applied uniformly to the existing states too.
 	bestRank := checkSeverityRank(stateOK)
@@ -383,7 +384,7 @@ func (m *Monitor) UpdateStatusFromChecks() {
 	// log.Println("state", m.State, "active event:", evt.ID)
 
 	for _, check := range checks { //nolint:gocritic // range copy is acceptable here
-		if check.State == stateERR || check.State == stateFail {
+		if check.State == stateERR {
 			evt.ChecksDown = append(evt.ChecksDown, check.Kind)
 			evt.Checks = append(evt.Checks, check)
 			if check.Error != nil {
@@ -419,7 +420,7 @@ func (m *Monitor) UpdateStatusFromChecks() {
 				return
 			}
 		}
-	case stateERR, stateFail:
+	case stateERR:
 		if evt.ID == 0 {
 			tn := time.Now()
 			evt.StartTime = &tn
@@ -500,7 +501,7 @@ func (m *Monitor) syncStatusPageIncidentsTx(tx *gorm.DB, event *Event) error {
 		page := &pages[i]
 		var incident StatusPageIncident
 		err := tx.Where("status_page_id = ? AND event_id = ?", page.ID, event.ID).First(&incident).Error
-		if m.State == stateERR || m.State == "FAIL" {
+		if m.State == stateERR {
 			if err != nil {
 				// The database uniqueness constraint makes concurrent state updates idempotent.
 				incident = StatusPageIncident{StatusPageID: page.ID, EventID: &event.ID, Title: m.GetLabel() + " is unavailable", BodyMD: event.Reason, Severity: StatusPageIncidentSeverityCrit, StartedAt: time.Now()}