refactor(config): migrate to SDKConfig and streamline proxy handling

- Replaced `config.Config` with `config.SDKConfig` across components for simpler configuration management.
- Updated proxy setup functions and handlers to align with `SDKConfig` improvements.
- Reorganized handler imports to match new SDK structure.

internal/util/provider.go

@@ -26,7 +26,7 @@ import (
 //
 // Returns:
 //   - []string: All provider identifiers capable of serving the model, ordered by preference.
-func GetProviderName(modelName string, cfg *config.Config) []string {
+func GetProviderName(modelName string) []string {
 	if modelName == "" {
 		return nil
 	}

internal/util/proxy.go

@@ -9,7 +9,7 @@ import (
 	"net/http"
 	"net/url"
 
-	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+	"github.com/router-for-me/CLIProxyAPI/v6/sdk/config"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/proxy"
 )
@@ -17,7 +17,7 @@ import (
 // SetProxy configures the provided HTTP client with proxy settings from the configuration.
 // It supports SOCKS5, HTTP, and HTTPS proxies. The function modifies the client's transport
 // to route requests through the configured proxy server.
-func SetProxy(cfg *config.Config, httpClient *http.Client) *http.Client {
+func SetProxy(cfg *config.SDKConfig, httpClient *http.Client) *http.Client {
 	var transport *http.Transport
 	// Attempt to parse the proxy URL from the configuration.
 	proxyURL, errParse := url.Parse(cfg.ProxyURL)