fix: avoid mutating global http.DefaultClient in webhook proxy (#2145)

Fixes a bug where the webhook HTTP client was mutating `http.DefaultClient` (the global singleton), causing ALL HTTP requests in the application to use the webhook proxy. This broke OIDC authentication and other external HTTP calls when webhook proxy was configured.

Fixes #2144

pkg/models/webhooks.go

@@ -245,7 +245,7 @@ func getWebhookHTTPClient() (client *http.Client) {
 		return webhookClient
 	}
 
-	client = http.DefaultClient
+	client = &http.Client{}
 	client.Timeout = time.Duration(config.WebhooksTimeoutSeconds.GetInt()) * time.Second
 
 	if config.WebhooksProxyURL.GetString() == "" || config.WebhooksProxyPassword.GetString() == "" {

pkg/modules/avatar/gravatar/gravatar.go

@@ -90,7 +90,7 @@ func (g *Provider) GetAvatar(user *user.User, size int64) ([]byte, string, error
 		if err != nil {
 			return nil, err
 		}
-		resp, err := http.DefaultClient.Do(req)
+		resp, err := (&http.Client{}).Do(req)
 		if err != nil {
 			return nil, err
 		}

pkg/modules/background/unsplash/proxy.go

@@ -30,7 +30,7 @@ func unsplashImage(url string, c echo.Context) error {
 	if err != nil {
 		return err
 	}
-	resp, err := http.DefaultClient.Do(req)
+	resp, err := (&http.Client{}).Do(req)
 	if err != nil {
 		return err
 	}

pkg/modules/background/unsplash/unsplash.go

@@ -257,7 +257,7 @@ func (p *Provider) Set(s *xorm.Session, image *background.Image, project *models
 	if err != nil {
 		return
 	}
-	resp, err := http.DefaultClient.Do(req)
+	resp, err := (&http.Client{}).Do(req)
 	if err != nil {
 		return err
 	}
@@ -340,7 +340,7 @@ func pingbackByPhotoID(photoID string) {
 	if err != nil {
 		log.Errorf("Unsplash Pingback Failed: %s", err.Error())
 	}
-	_, err = http.DefaultClient.Do(req)
+	_, err = (&http.Client{}).Do(req)
 	if err != nil {
 		log.Errorf("Unsplash Pingback Failed: %s", err.Error())
 	}

pkg/modules/migration/microsoft-todo/microsoft_todo.go

@@ -187,7 +187,7 @@ func makeAuthenticatedGetRequest(token, urlPart string, v interface{}) error {
 	}
 	req.Header.Set("Authorization", "Bearer "+token)
 
-	resp, err := http.DefaultClient.Do(req)
+	resp, err := (&http.Client{}).Do(req)
 	if err != nil {
 		return err
 	}

pkg/utils/avatar.go

@@ -101,7 +101,7 @@ func DownloadImage(url string) ([]byte, error) {
 		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
 	}
 
-	resp, err := http.DefaultClient.Do(req)
+	resp, err := (&http.Client{}).Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("failed to download image: %w", err)
 	}