build: update Go to 1.27.1 and modernize the codebase (#2798)

Toolchain and CI:
- Bump go directive from 1.26.8 to 1.27.1 (go.mod)
- Use golang:1.27-alpine builder images in all Dockerfiles
- Bump golangci-lint to v2.13.2 (first release with go1.27 support)
- Add CI gate: `go fix -diff` fails when outdated Go patterns are
  detected (locally: `make check-modernize`)

Note: darwin binaries now require macOS 13 or later.

Lint fixes required by golangci-lint v2.13.2:
- goconst: ignore tests (all 436 findings were test-only; goconst
  got stricter since v2.12 and this option was added for it)
- openai.go: keep deprecated MaxTokens deliberately with a nolint
  rationale (max_tokens is the only form universally supported by
  OpenAI-compatible backends like One-API, LiteLLM, Ollama shim)
- state.go: drop always-nil flags param from appendChartVersionFlags
  (renamed to chartVersionFlags, unparam)

Modernization (go fix ./..., 62 files):
- interface{} -> any, maps.Copy, strings.SplitSeq, range-over-int,
  builtin min/max, slices.Contains/ContainsFunc/Sort, WaitGroup.Go,
  reflect.Type.Fields(), new(expr)
- exit_error.go: strings.Builder + fmt.Fprintf instead of string
  concatenation and WriteString(fmt.Sprintf(...)) (QF1012)
- chart_dependency.go: strings.CutLast for OCI dependency helpers

Signed-off-by: yxxhero <aiopsclub@163.com>
Co-authored-by: Claude <noreply@anthropic.com>

pkg/app/init_test.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"slices"
 	"strings"
 	"testing"
 
@@ -143,10 +144,8 @@ func createPluginYAML(t *testing.T, pluginsDir, pluginDirName, name, version str
 func newHelmPluginMockRunner(pluginErr error) *initMockRunner {
 	return &initMockRunner{
 		executeFunc: func(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
-			for _, a := range args {
-				if a == "--short" {
-					return []byte("v3.18.6"), nil
-				}
+			if slices.Contains(args, "--short") {
+				return []byte("v3.18.6"), nil
 			}
 			// Fail any "helm plugin ..." subcommand (install, update, etc.)
 			if len(args) > 0 && args[0] == "plugin" {
@@ -168,10 +167,8 @@ func TestCheckHelmPlugins_InstallErrorButPluginPresent(t *testing.T) {
 	// plugin.yaml on disk and then returns an error.
 	runner := &initMockRunner{
 		executeFunc: func(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
-			for _, a := range args {
-				if a == "--short" {
-					return []byte("v3.18.6"), nil
-				}
+			if slices.Contains(args, "--short") {
+				return []byte("v3.18.6"), nil
 			}
 			if len(args) > 0 && args[0] == "plugin" && len(args) >= 3 && args[1] == "install" {
 				// Find which plugin is being installed by matching the repo URL.
@@ -228,10 +225,8 @@ func TestCheckHelmPlugins_UpdateUsesUninstallReinstall(t *testing.T) {
 	// that writes the required version to disk.
 	runner := &initMockRunner{
 		executeFunc: func(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
-			for _, a := range args {
-				if a == "--short" {
-					return []byte("v3.18.6"), nil
-				}
+			if slices.Contains(args, "--short") {
+				return []byte("v3.18.6"), nil
 			}
 			if len(args) >= 2 && args[0] == "plugin" {
 				switch args[1] {
@@ -309,10 +304,8 @@ func TestCheckHelmPlugins_UpdateErrorButPluginAtRequiredVersion(t *testing.T) {
 	// verifies the version and warns instead of returning an error.
 	runner := &initMockRunner{
 		executeFunc: func(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
-			for _, a := range args {
-				if a == "--short" {
-					return []byte("v3.18.6"), nil
-				}
+			if slices.Contains(args, "--short") {
+				return []byte("v3.18.6"), nil
 			}
 			if len(args) >= 2 && args[0] == "plugin" {
 				switch args[1] {