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- Add CI gate: `go fix -diff` fails when outdated Go patterns are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/tmpl/context_tmpl.go

@@ -3,6 +3,7 @@ package tmpl
 import (
 	"bytes"
 	"fmt"
+	"maps"
 	"path/filepath"
 	"strings"
 	"text/template"
@@ -36,14 +37,10 @@ func (c *Context) CreateFuncMap() template.FuncMap {
 	}
 
 	// add functions from the Context's createFuncMap() method to the funcMap
-	for name, f := range c.createFuncMap() {
-		funcMap[name] = f
-	}
+	maps.Copy(funcMap, c.createFuncMap())
 
 	// add aliased functions to the funcMap
-	for name, f := range aliased {
-		funcMap[name] = f
-	}
+	maps.Copy(funcMap, aliased)
 
 	return funcMap
 }
@@ -90,7 +87,7 @@ func (c *Context) newTemplate() (*template.Template, error) {
 	includedNames := make(map[string]int)
 
 	// Add the 'include' function here so we can close over t.
-	funcMap["include"] = func(name string, data interface{}) (string, error) {
+	funcMap["include"] = func(name string, data any) (string, error) {
 		var buf strings.Builder
 		if v, ok := includedNames[name]; ok {
 			if v > recursionMaxNums {

pkg/tmpl/context_tmpl_test.go

@@ -404,7 +404,7 @@ func TestContext_RenderTemplateToBuffer(t *testing.T) {
 		},
 	}
 	s := "Hello, {{ include \"name\" . }}!"
-	data := map[string]interface{}{
+	data := map[string]any{
 		"Name": "Alice",
 	}
 	expected := "Hello, Alice!"