feat(M35): dynamic target configuration with encrypted config, test connection, and GUI updates

Mirror M34's dynamic issuer config pattern for deployment targets: AES-256-GCM
encrypted config storage, sensitive field redaction in API responses, agent
heartbeat-based test connection endpoint, and full frontend updates including
test status indicators, source badges, and removal of stale hostname/status
fields from the Target interface.

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

internal/api/handler/target_handler_test.go

@@ -13,11 +13,12 @@ import (
 
 // MockTargetService is a mock implementation of TargetService interface.
 type MockTargetService struct {
-	ListTargetsFn  func(page, perPage int) ([]domain.DeploymentTarget, int64, error)
-	GetTargetFn    func(id string) (*domain.DeploymentTarget, error)
-	CreateTargetFn func(target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
-	UpdateTargetFn func(id string, target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
-	DeleteTargetFn func(id string) error
+	ListTargetsFn        func(page, perPage int) ([]domain.DeploymentTarget, int64, error)
+	GetTargetFn          func(id string) (*domain.DeploymentTarget, error)
+	CreateTargetFn       func(target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
+	UpdateTargetFn       func(id string, target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
+	DeleteTargetFn       func(id string) error
+	TestTargetConnectionFn func(id string) error
 }
 
 func (m *MockTargetService) ListTargets(page, perPage int) ([]domain.DeploymentTarget, int64, error) {
@@ -55,6 +56,13 @@ func (m *MockTargetService) DeleteTarget(id string) error {
 	return nil
 }
 
+func (m *MockTargetService) TestTargetConnection(id string) error {
+	if m.TestTargetConnectionFn != nil {
+		return m.TestTargetConnectionFn(id)
+	}
+	return nil
+}
+
 func TestListTargets_Success(t *testing.T) {
 	now := time.Now()
 	t1 := domain.DeploymentTarget{
@@ -419,3 +427,69 @@ func TestDeleteTarget_EmptyID(t *testing.T) {
 		t.Fatalf("expected status 400, got %d", w.Code)
 	}
 }
+
+func TestTestTargetConnection_Success(t *testing.T) {
+	mock := &MockTargetService{
+		TestTargetConnectionFn: func(id string) error {
+			return nil
+		},
+	}
+
+	handler := NewTargetHandler(mock)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/targets/t-nginx-01/test", nil)
+	req = req.WithContext(contextWithRequestID())
+	w := httptest.NewRecorder()
+
+	handler.TestTargetConnection(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected status 200, got %d", w.Code)
+	}
+
+	var resp map[string]interface{}
+	if err := json.NewDecoder(w.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp["status"] != "success" {
+		t.Errorf("expected status 'success', got %v", resp["status"])
+	}
+}
+
+func TestTestTargetConnection_Failed(t *testing.T) {
+	mock := &MockTargetService{
+		TestTargetConnectionFn: func(id string) error {
+			return ErrMockServiceFailed
+		},
+	}
+
+	handler := NewTargetHandler(mock)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/targets/t-nginx-01/test", nil)
+	req = req.WithContext(contextWithRequestID())
+	w := httptest.NewRecorder()
+
+	handler.TestTargetConnection(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected status 200, got %d", w.Code)
+	}
+
+	var resp map[string]interface{}
+	if err := json.NewDecoder(w.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+	if resp["status"] != "failed" {
+		t.Errorf("expected status 'failed', got %v", resp["status"])
+	}
+}
+
+func TestTestTargetConnection_MethodNotAllowed(t *testing.T) {
+	handler := NewTargetHandler(&MockTargetService{})
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/targets/t-nginx-01/test", nil)
+	w := httptest.NewRecorder()
+
+	handler.TestTargetConnection(w, req)
+
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Fatalf("expected status 405, got %d", w.Code)
+	}
+}

internal/api/handler/targets.go

@@ -17,6 +17,7 @@ type TargetService interface {
 	CreateTarget(target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
 	UpdateTarget(id string, target domain.DeploymentTarget) (*domain.DeploymentTarget, error)
 	DeleteTarget(id string) error
+	TestTargetConnection(id string) error
 }
 
 // TargetHandler handles HTTP requests for deployment target operations.
@@ -189,3 +190,36 @@ func (h TargetHandler) DeleteTarget(w http.ResponseWriter, r *http.Request) {
 
 	w.WriteHeader(http.StatusNoContent)
 }
+
+// TestTargetConnection tests target connectivity by checking the assigned agent's heartbeat.
+// POST /api/v1/targets/{id}/test
+func (h TargetHandler) TestTargetConnection(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		Error(w, http.StatusMethodNotAllowed, "Method not allowed")
+		return
+	}
+
+	requestID := middleware.GetRequestID(r.Context())
+
+	// Extract target ID from path: /api/v1/targets/{id}/test
+	path := strings.TrimPrefix(r.URL.Path, "/api/v1/targets/")
+	parts := strings.Split(path, "/")
+	if len(parts) < 2 || parts[0] == "" {
+		ErrorWithRequestID(w, http.StatusBadRequest, "Target ID is required", requestID)
+		return
+	}
+	id := parts[0]
+
+	if err := h.svc.TestTargetConnection(id); err != nil {
+		JSON(w, http.StatusOK, map[string]interface{}{
+			"status":  "failed",
+			"message": err.Error(),
+		})
+		return
+	}
+
+	JSON(w, http.StatusOK, map[string]interface{}{
+		"status":  "success",
+		"message": "Agent is online and reachable",
+	})
+}