refactor(architecture): eliminate internal package and complete cordis single-owner model and repository migration

- Physically purged all legacy internal/ packages, centralized pkg/model/ and pkg/repository/
- Migrated domain models and database repositories into self-contained owner plugins (user, auth, message_gateway, admin, upload, risk_control)
- Decoupled cross-plugin interactions via pure core/contracts and typed EventBus
- Ensured 100% test coverage pass, zero data races (-race clean), and 0 lint issues in make code-check

pkg/task/scheduler/scheduler_test.go

@@ -0,0 +1,42 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package scheduler
+
+import "testing"
+
+func TestWaitForStop(t *testing.T) {
+	tests := []struct {
+		name        string
+		closeDone   bool
+		closeSignal bool
+		wantSignal  bool
+	}{
+		{
+			name:      "explicit stop",
+			closeDone: true,
+		},
+		{
+			name:        "process signal",
+			closeSignal: true,
+			wantSignal:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			done := make(chan struct{})
+			signals := make(chan struct{})
+			if tt.closeDone {
+				close(done)
+			}
+			if tt.closeSignal {
+				close(signals)
+			}
+
+			if got := waitForStop(done, signals); got != tt.wantSignal {
+				t.Errorf("waitForStop() = %t, want %t", got, tt.wantSignal)
+			}
+		})
+	}
+}