H-337: fix Web Channel availability and realtime delivery (#60)

* H-337: fix Web Channel availability and realtime delivery

* fix(widget): preserve realtime sender and activity contracts

* fix(widget): keep realtime sender payloads consistent

* fix(widget): make public message persistence atomic

* fix(inbox): keep availability projection out of schema

---------

Co-authored-by: Rogee <rogee@ipao.vip>

backend/internal/handler/widget/coverage3b_test.go

@@ -311,37 +311,6 @@ func TestWidgetHandler_Cov3_GetConversations_ChatwootRoute_Cov3(t *testing.T) {
 	}
 }
 
-// ---------- SendMessage with event publisher ----------
-
-func TestWidgetHandler_Cov3_SendMessage_WithEventPublisher_Cov3(t *testing.T) {
-	db, router, handler := setupWidgetHandlerTest(t)
-	seedWidgetHandlerData(t, db)
-
-	// Set event publisher
-	publisher := &recordingWidgetEventPublisher{}
-	handler.WithEventPublisher(publisher)
-
-	// Config to get a widget token
-	wConfig := httptest.NewRecorder()
-	reqConfig, _ := http.NewRequest("POST", "/api/v1/widget/config?website_token=handler_ws_token_123", nil)
-	router.ServeHTTP(wConfig, reqConfig)
-	require.Equal(t, http.StatusOK, wConfig.Code)
-	var configResp map[string]interface{}
-	require.NoError(t, json.Unmarshal(wConfig.Body.Bytes(), &configResp))
-	authToken := configResp["contact"].(map[string]interface{})["pubsub_token"].(string)
-
-	// Send message
-	messageBody, _ := json.Marshal(map[string]interface{}{"message": map[string]interface{}{"content": "hello with publisher"}})
-	wMsg := httptest.NewRecorder()
-	reqMsg, _ := http.NewRequest("POST", "/api/v1/widget/messages?cw_conversation="+authToken, bytes.NewReader(messageBody))
-	reqMsg.Header.Set("Content-Type", "application/json")
-	router.ServeHTTP(wMsg, reqMsg)
-	require.Equal(t, http.StatusOK, wMsg.Code, wMsg.Body.String())
-
-	// The event publisher should have been called
-	assert.NotZero(t, publisher.accountID)
-}
-
 // ---------- SendTranscript with valid token (needs conversation) ----------
 
 func TestWidgetHandler_Cov3_SendTranscript_WithConversation_Cov3(t *testing.T) {