test: atomic counter in notifier countingSink

Dispatch fires sinks in goroutines; the plain-int counter tripped
go test -race. CI red since the notification bell landed.

server/internal/services/notifier/notifier_test.go

@@ -2,6 +2,7 @@ package notifier
 
 import (
 	"context"
+	"sync/atomic"
 	"testing"
 	"time"
 )
@@ -86,8 +87,8 @@ func TestDispatcherDedup(t *testing.T) {
 	// Let goroutines settle.
 	time.Sleep(20 * time.Millisecond)
 
-	if cs.count != 1 {
-		t.Errorf("expected exactly 1 delivery (dedup suppressed the rest), got %d", cs.count)
+	if cs.count.Load() != 1 {
+		t.Errorf("expected exactly 1 delivery (dedup suppressed the rest), got %d", cs.count.Load())
 	}
 }
 
@@ -106,17 +107,17 @@ func TestDispatcherNoDedupDifferentFP(t *testing.T) {
 
 	time.Sleep(20 * time.Millisecond)
 
-	if cs.count != 2 {
-		t.Errorf("expected 2 deliveries for different fingerprints, got %d", cs.count)
+	if cs.count.Load() != 2 {
+		t.Errorf("expected 2 deliveries for different fingerprints, got %d", cs.count.Load())
 	}
 }
 
 type countingSink struct {
-	count int
+	count atomic.Int64
 }
 
 func (s *countingSink) ID() string { return "test" }
 func (s *countingSink) Send(_ context.Context, _ NotifyEvent) error {
-	s.count++
+	s.count.Add(1)
 	return nil
 }