refactor(msg_gateway): decouple bot gateway and push notification architecture

- Split shared monolithic consts into bot, push, and errs with typed sentinel errors
- Restructure model layer into distinct bot and push subdomains
- Refactor DAO layer to enforce single-owner principle and remove cross-table raw SQL queries
- Decompose 1150+ line service/push.go into push_channel, push_event, push_trigger, push_worker, and push_template
- Clean up controller layer with generic request handlers and parameter validation in controller/base.go
- Streamline plugin.go to core Cordis lifecycle orchestration and remove re-export bloat
- Verify all unit tests, race tests, Cordis architecture rules, and Swagger generation pass cleanly

backend/plugins/domain/msg_gateway/service/bot_dispatch_test.go

@@ -0,0 +1,46 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package service_test
+
+import (
+	"Wavelet/plugins/domain/msg_gateway/dao"
+	"Wavelet/plugins/domain/msg_gateway/model/entity"
+	"Wavelet/plugins/domain/msg_gateway/service"
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/glebarez/sqlite"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
+)
+
+type dispatchTestDB struct{ db *gorm.DB }
+
+func (m *dispatchTestDB) GORM() *gorm.DB                  { return m.db }
+func (m *dispatchTestDB) DB(ctx context.Context) *gorm.DB { return m.db.WithContext(ctx) }
+func (m *dispatchTestDB) Named(_ string) *gorm.DB         { return m.db }
+
+func TestBotDispatchValidatePayload(t *testing.T) {
+	h := &service.BotDispatchHandler{}
+	_, err := h.ValidatePayload([]byte(`{}`))
+	require.Error(t, err)
+	_, err = h.ValidatePayload([]byte(`{"text":"hello"}`))
+	require.NoError(t, err)
+}
+
+func TestBotDispatchNoChannels(t *testing.T) {
+	testDB, err := gorm.Open(sqlite.Open(filepath.Join(t.TempDir(), "dispatch.db")), &gorm.Config{})
+	require.NoError(t, err)
+	require.NoError(t, testDB.AutoMigrate(&entity.MessageChannel{}, &entity.MessageBinding{}))
+	dao.SetDBServiceForTest(&dispatchTestDB{db: testDB})
+	t.Cleanup(func() { dao.SetDBServiceForTest(nil) })
+
+	h := &service.BotDispatchHandler{}
+	res, err := h.Execute(context.Background(), []byte(`{"text":"hello"}`))
+	require.NoError(t, err)
+	require.NotNil(t, res)
+	assert.Contains(t, res.Message, "成功 0")
+}