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/meta_test.go

@@ -0,0 +1,35 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package task_test
+
+import (
+	"testing"
+
+	"github.com/Rain-kl/Wavelet/pkg/task"
+)
+
+func TestDuplicateTaskMeta(t *testing.T) {
+	dummyMeta := task.TaskMeta{
+		Type:      "test_duplicate_task",
+		AsynqTask: "test:duplicate_task",
+		Name:      "Test Duplicate Task",
+	}
+
+	task.RegisterTaskMeta(dummyMeta)
+	task.RegisterTaskMeta(dummyMeta)
+
+	metas := task.GetDispatchableTasks()
+
+	// Check if we have duplicates by checking if a Type appears more than once
+	seen := make(map[string]int)
+	for _, m := range metas {
+		seen[m.Type]++
+	}
+
+	for taskType, count := range seen {
+		if count > 1 {
+			t.Errorf("Task type %q registered %d times, expected at most 1", taskType, count)
+		}
+	}
+}