feat(pluginhost, api): add support for "X-CPA-SUPPORT-PLUGIN" header with CGO detection

- Introduced `SupportPluginHeaderValue` to indicate CGO build status (`1` for enabled, `0` for disabled).
- Updated API response headers in `handler.go` to include "X-CPA-SUPPORT-PLUGIN".
- Added unit tests to verify proper header behavior under varying conditions.

internal/api/handlers/management/handler.go

@@ -171,6 +171,7 @@ func (h *Handler) Middleware() gin.HandlerFunc {
 		c.Header("X-CPA-VERSION", buildinfo.Version)
 		c.Header("X-CPA-COMMIT", buildinfo.Commit)
 		c.Header("X-CPA-BUILD-DATE", buildinfo.BuildDate)
+		c.Header("X-CPA-SUPPORT-PLUGIN", pluginhost.SupportPluginHeaderValue())
 
 		clientIP := c.ClientIP()
 		localClient := clientIP == "127.0.0.1" || clientIP == "::1"

internal/api/handlers/management/handler_test.go

@@ -2,10 +2,13 @@ package management
 
 import (
 	"net/http"
+	"net/http/httptest"
 	"strings"
 	"testing"
 
+	"github.com/gin-gonic/gin"
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/pluginhost"
 )
 
 func TestAuthenticateManagementKey_LocalhostIPBan_BlocksCorrectKeyDuringBan(t *testing.T) {
@@ -36,3 +39,51 @@ func TestAuthenticateManagementKey_LocalhostIPBan_BlocksCorrectKeyDuringBan(t *t
 		t.Fatalf("unexpected banned message: %q", errMsg)
 	}
 }
+
+func TestMiddlewareSetsSupportPluginHeader(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	h := &Handler{
+		cfg:            &config.Config{},
+		failedAttempts: make(map[string]*attemptInfo),
+		envSecret:      "test-secret",
+	}
+	middleware := h.Middleware()
+
+	t.Run("invalid key", func(t *testing.T) {
+		rec := httptest.NewRecorder()
+		c, _ := gin.CreateTestContext(rec)
+		c.Request = httptest.NewRequest(http.MethodGet, "/v0/management/config", nil)
+		c.Request.RemoteAddr = "127.0.0.1:12345"
+		c.Request.Header.Set("X-Management-Key", "wrong-secret")
+
+		middleware(c)
+
+		if rec.Code != http.StatusUnauthorized {
+			t.Fatalf("status = %d, want %d", rec.Code, http.StatusUnauthorized)
+		}
+		if got := rec.Header().Get("X-CPA-SUPPORT-PLUGIN"); got != pluginhost.SupportPluginHeaderValue() {
+			t.Fatalf("X-CPA-SUPPORT-PLUGIN = %q, want %q", got, pluginhost.SupportPluginHeaderValue())
+		}
+	})
+
+	t.Run("valid key", func(t *testing.T) {
+		engine := gin.New()
+		engine.GET("/v0/management/config", middleware, func(c *gin.Context) {
+			c.Status(http.StatusOK)
+		})
+
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/v0/management/config", nil)
+		req.RemoteAddr = "127.0.0.1:12345"
+		req.Header.Set("X-Management-Key", "test-secret")
+		engine.ServeHTTP(rec, req)
+
+		if rec.Code != http.StatusOK {
+			t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+		}
+		if got := rec.Header().Get("X-CPA-SUPPORT-PLUGIN"); got != pluginhost.SupportPluginHeaderValue() {
+			t.Fatalf("X-CPA-SUPPORT-PLUGIN = %q, want %q", got, pluginhost.SupportPluginHeaderValue())
+		}
+	})
+}

internal/pluginhost/support.go

@@ -0,0 +1,6 @@
+package pluginhost
+
+// SupportPluginHeaderValue reports whether the current binary was built with CGO enabled.
+func SupportPluginHeaderValue() string {
+	return supportPluginValue
+}

internal/pluginhost/support_cgo.go

@@ -0,0 +1,5 @@
+//go:build cgo
+
+package pluginhost
+
+const supportPluginValue = "1"

internal/pluginhost/support_nocgo.go

@@ -0,0 +1,5 @@
+//go:build !cgo
+
+package pluginhost
+
+const supportPluginValue = "0"