fix: 改进 notifier 包的错误处理和连接复用

- notifier.go: Send 使用 errors.Join 收集所有通道的错误，不再丢弃中间错误
- bark.go/gotify.go/webhook.go: 响应体在关闭前先 drain，确保 HTTP 连接可复用

Co-authored-by: HoshinoAya <HoshinoDesu@users.noreply.github.com>

internal/notifier/bark.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 
 	"github.com/CyberPigeon/internal/config"
@@ -55,7 +56,10 @@ func (b *BarkChannel) Send(msg Message) error {
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+	defer func() {
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+	}()
 
 	if resp.StatusCode != http.StatusOK {
 		return fmt.Errorf("Bark 返回错误状态: %d", resp.StatusCode)

internal/notifier/gotify.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 
 	"github.com/CyberPigeon/internal/config"
@@ -61,7 +62,10 @@ func (g *GotifyChannel) Send(msg Message) error {
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+	defer func() {
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+	}()
 
 	if resp.StatusCode != http.StatusOK {
 		return fmt.Errorf("Gotify 返回错误状态: %d", resp.StatusCode)

internal/notifier/notifier.go

@@ -1,6 +1,7 @@
 package notifier
 
 import (
+	"errors"
 	"fmt"
 	"log/slog"
 	"sync"
@@ -95,14 +96,7 @@ func (n *Notifier) Send(msg Message) error {
 
 	wg.Wait()
 
-	// 返回最后一个错误
-	var lastErr error
-	for _, err := range errs {
-		if err != nil {
-			lastErr = err
-		}
-	}
-	return lastErr
+	return errors.Join(errs...)
 }
 
 // createChannel 根据配置创建通道

internal/notifier/webhook.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@@ -139,7 +140,10 @@ func (w *WebhookChannel) Send(msg Message) error {
 	if err != nil {
 		return err
 	}
-	defer resp.Body.Close()
+	defer func() {
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+	}()
 
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		return fmt.Errorf("Webhook 返回错误状态: %d", resp.StatusCode)