fix: clean up remaining session store references and test dependencies

Remove any remaining SessionStore interface definitions and fix test
configurations to work with the new stateless architecture.

weed/iam/sts/sts_service_test.go

@@ -307,11 +307,11 @@ func setupTestSTSService(t *testing.T) *STSService {
 	service := NewSTSService()
 
 	config := &STSConfig{
-		TokenDuration:      time.Hour,
-		MaxSessionLength:   time.Hour * 12,
-		Issuer:            "test-sts",
-		SigningKey:        []byte("test-signing-key-32-characters-long"),
-		SessionStoreType:  "memory", // Use memory store for unit tests
+		TokenDuration:    time.Hour,
+		MaxSessionLength: time.Hour * 12,
+		Issuer:           "test-sts",
+		SigningKey:       []byte("test-signing-key-32-characters-long"),
+		SessionStoreType: "memory", // Use memory store for unit tests
 	}
 
 	err := service.Initialize(config)