feat(config): support HTTP headers across providers

internal/runtime/executor/gemini_executor.go

@@ -495,44 +495,11 @@ func resolveGeminiBaseURL(auth *cliproxyauth.Auth) string {
 }
 
 func applyGeminiHeaders(req *http.Request, auth *cliproxyauth.Auth) {
-	if req == nil {
-		return
+	var attrs map[string]string
+	if auth != nil {
+		attrs = auth.Attributes
 	}
-	headers := geminiCustomHeaders(auth)
-	if len(headers) == 0 {
-		return
-	}
-	for k, v := range headers {
-		if k == "" || v == "" {
-			continue
-		}
-		req.Header.Set(k, v)
-	}
-}
-
-func geminiCustomHeaders(auth *cliproxyauth.Auth) map[string]string {
-	if auth == nil || auth.Attributes == nil {
-		return nil
-	}
-	headers := make(map[string]string, len(auth.Attributes))
-	for k, v := range auth.Attributes {
-		if !strings.HasPrefix(k, "header:") {
-			continue
-		}
-		name := strings.TrimSpace(strings.TrimPrefix(k, "header:"))
-		if name == "" {
-			continue
-		}
-		val := strings.TrimSpace(v)
-		if val == "" {
-			continue
-		}
-		headers[name] = val
-	}
-	if len(headers) == 0 {
-		return nil
-	}
-	return headers
+	util.ApplyCustomHeadersFromAttrs(req, attrs)
 }
 
 func fixGeminiImageAspectRatio(modelName string, rawJSON []byte) []byte {