fix: respect proxy env vars in runner client

Fixes #957.

Co-Authored-By: Codet GPT-5 <codet@commitgo.local>

internal/pkg/client/http.go

@@ -17,6 +17,7 @@ import (
 
 func getHTTPClient(endpoint string, insecure bool) *http.Client {
 	transport := &http.Transport{
+		Proxy:               http.ProxyFromEnvironment,
 		MaxIdleConns:        10,
 		MaxIdleConnsPerHost: 10, // All requests go to one host; default is 2 which causes frequent reconnects.
 		IdleConnTimeout:     90 * time.Second,

internal/pkg/client/http_test.go

@@ -0,0 +1,27 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package client
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetHTTPClientUsesProxyFromEnvironment(t *testing.T) {
+	t.Setenv("HTTP_PROXY", "http://proxy.example.com:8080")
+
+	client := getHTTPClient("http://gitea.example.com", false)
+	transport, ok := client.Transport.(*http.Transport)
+	require.True(t, ok)
+
+	req, err := http.NewRequest(http.MethodGet, "http://gitea.example.com/api/actions/ping", nil)
+	require.NoError(t, err)
+
+	proxyURL, err := transport.Proxy(req)
+	require.NoError(t, err)
+	require.NotNil(t, proxyURL)
+	require.Equal(t, "http://proxy.example.com:8080", proxyURL.String())
+}