feat: enhance Safew error handling and polling mechanism

- Added error_msg field to safewAPIResponse for better error descriptions.
- Updated safewErrorDescription function to include error_msg in the output.
- Introduced a new test to verify that error messages are included in Safew error descriptions.
- Improved the polling mechanism in the Watcher to handle conflicts and ensure no overlapping polls occur.

internal/adapter/safew.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"time"
 )
 
 const safewAPIBase = "https://api.safew.bot"
@@ -29,6 +30,7 @@ type safewMessage struct {
 type safewAPIResponse struct {
 	OK          bool   `json:"ok"`
 	Description string `json:"description"`
+	ErrorMsg    string `json:"error_msg"`
 }
 
 func (s *SafeWSender) Type() string { return "safew" }
@@ -112,17 +114,22 @@ func (e *SafewAuthError) Error() string {
 	return e.Description
 }
 
+var safewLongPollClient = &http.Client{Timeout: 45 * time.Second}
+
 func (s *SafeWSender) PollGroupChats(token string, offset int64, timeout int) ([]SafewChat, int64, error) {
 	token = strings.TrimSpace(token)
 	if token == "" {
 		return nil, offset, fmt.Errorf("safew: token is required")
 	}
-	reqBody, _ := json.Marshal(map[string]any{
+	payload := map[string]any{
 		"timeout": timeout,
-		"offset":  offset,
 		"limit":   100,
-	})
-	resp, err := http.Post(s.methodURL(token, "getUpdates"), "application/json", bytes.NewReader(reqBody))
+	}
+	if offset > 0 {
+		payload["offset"] = offset
+	}
+	reqBody, _ := json.Marshal(payload)
+	resp, err := safewLongPollClient.Post(s.methodURL(token, "getUpdates"), "application/json", bytes.NewReader(reqBody))
 	if err != nil {
 		return nil, offset, fmt.Errorf("safew getUpdates: %w", err)
 	}
@@ -183,7 +190,14 @@ func safewErrorDescription(body []byte) string {
 	if err := json.Unmarshal(body, &api); err != nil {
 		return strings.TrimSpace(string(body))
 	}
-	return api.Description
+	switch {
+	case api.Description != "" && api.ErrorMsg != "":
+		return api.Description + ": " + api.ErrorMsg
+	case api.ErrorMsg != "":
+		return api.ErrorMsg
+	default:
+		return api.Description
+	}
 }
 
 func escapeMarkdownV2(s string) string {