Update proxy to Zhanlu v1.4.2 provider flow

The 1.4.2 extension replaced the old signed/encrypted chat gateway with an
OpenAI-compatible aigateway. Align the proxy with the new flow:

- Use ecloud.10086.cn login/model base URLs, zhanlu_ide plugin headers and
  v1.4.2 plugin version
- Provision the model API key via SM2-signed get-or-create after v1/login
  profile fetch; store api_key/model_base_url/email in credentials
- Chat via Bearer apiKey against {modelBaseUrl}/chat/completions with plain
  OpenAI SSE passthrough; fetch /v1/models from the gateway model-info endpoint
- Force HTTP/1.1 upstream (gateway drops HTTP/2 ALPN negotiation with EOF)
- Drop obsolete AES body encryption, model name mapping and vscode headers

internal/auth/credentials.go

@@ -10,14 +10,30 @@ import (
 )
 
 type Credentials struct {
-	AccessKey string    `json:"access_key"`
-	SecretKey string    `json:"secret_key"`
-	Token     string    `json:"token"`
-	BaseURL   string    `json:"base_url,omitempty"`
-	SavedAt   time.Time `json:"saved_at"`
+	AccessKey    string    `json:"access_key"`
+	SecretKey    string    `json:"secret_key"`
+	Token        string    `json:"token"`
+	APIKey       string    `json:"api_key,omitempty"`
+	ModelBaseURL string    `json:"model_base_url,omitempty"`
+	Email        string    `json:"email,omitempty"`
+	Organization string    `json:"organization,omitempty"`
+	Team         string    `json:"team,omitempty"`
+	BaseURL      string    `json:"base_url,omitempty"`
+	SavedAt      time.Time `json:"saved_at"`
+}
+
+type Profile struct {
+	Email        string
+	Organization string
+	Team         string
+	UserName     string
+	Telephone    string
 }
 
 func (c Credentials) Validate() error {
+	if strings.TrimSpace(c.APIKey) != "" && strings.TrimSpace(c.ModelBaseURL) != "" {
+		return nil
+	}
 	if strings.TrimSpace(c.AccessKey) == "" {
 		return errors.New("access_key is required")
 	}
@@ -30,6 +46,10 @@ func (c Credentials) Validate() error {
 	return nil
 }
 
+func (c Credentials) HasAPIKey() bool {
+	return strings.TrimSpace(c.APIKey) != "" && strings.TrimSpace(c.ModelBaseURL) != ""
+}
+
 func LoadCredentials(path string) (Credentials, error) {
 	b, err := os.ReadFile(path)
 	if err != nil {