feat: 算力引擎 Go 后端核心（new-api）

- 统一 OpenAI 兼容 /v1 中继 + 渠道/额度/令牌/流水
- 各领域包：relay 模型网关、model 数据层、controller 管理 API

service/codex_channel_models.go

@@ -0,0 +1,81 @@
+package service
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/QuantumNous/new-api/constant"
+	"github.com/QuantumNous/new-api/model"
+)
+
+func FetchCodexChannelModels(channel *model.Channel) ([]string, error) {
+	if channel == nil || channel.Type != constant.ChannelTypeCodex {
+		return nil, fmt.Errorf("channel type is not Codex")
+	}
+	if channel.ChannelInfo.IsMultiKey {
+		return nil, fmt.Errorf("codex channel does not support multi-key model discovery")
+	}
+
+	client, err := NewProxyHttpClient(channel.GetSetting().Proxy)
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+
+	clientVersion, err := GetLatestCodexClientVersion(ctx, client)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get Codex client version: %w", err)
+	}
+
+	baseURL := channel.GetBaseURL()
+	if baseURL == "" {
+		baseURL = constant.ChannelBaseURLs[constant.ChannelTypeCodex]
+	}
+	return fetchCodexChannelModels(ctx, channel, baseURL, client, clientVersion)
+}
+
+func fetchCodexChannelModels(
+	ctx context.Context,
+	channel *model.Channel,
+	baseURL string,
+	client *http.Client,
+	clientVersion string,
+) ([]string, error) {
+	oauthKey, err := parseCodexOAuthKey(strings.TrimSpace(channel.Key))
+	if err != nil {
+		return nil, err
+	}
+
+	statusCode, models, err := FetchCodexModels(ctx, client, baseURL, oauthKey, clientVersion)
+	if err != nil {
+		return nil, err
+	}
+	if statusCode == http.StatusUnauthorized {
+		if channel.Id <= 0 {
+			return nil, fmt.Errorf("codex channel credential expired; save the channel before retrying model fetch")
+		}
+		refreshedKey, _, refreshErr := RefreshCodexChannelCredential(
+			ctx,
+			channel.Id,
+			CodexCredentialRefreshOptions{ResetCaches: true},
+		)
+		if refreshErr != nil {
+			return nil, fmt.Errorf("failed to refresh Codex channel credential: %w", refreshErr)
+		}
+		statusCode, models, err = FetchCodexModels(ctx, client, baseURL, &CodexOAuthKey{
+			AccessToken: refreshedKey.AccessToken,
+			AccountID:   refreshedKey.AccountID,
+		}, clientVersion)
+		if err != nil {
+			return nil, err
+		}
+	}
+	if statusCode < http.StatusOK || statusCode >= http.StatusMultipleChoices {
+		return nil, fmt.Errorf("upstream status: %d", statusCode)
+	}
+	return models, nil
+}