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/openai/types.go

@@ -28,21 +28,11 @@ func (r *ChatCompletionRequest) UnmarshalJSON(data []byte) error {
 }
 
 func (r ChatCompletionRequest) MarshalForUpstream() ([]byte, error) {
-	model := map[string]string{
-		"minimax-m2.5": "minimax-m25",
-		"glm4.7":       "glm47",
-	}[r.Model]
-	if model == "" {
-		model = r.Model
-	}
 	m := map[string]any{
-		"model":          model,
+		"model":          r.Model,
 		"messages":       r.Messages,
-		"temperature":    0,
 		"stream":         r.Stream,
 		"stream_options": map[string]any{"include_usage": true},
-		"max_tokens":     16000,
-		"inputs":         map[string]any{"aiDevQuestion": ""},
 	}
 	for k, v := range r.Extra {
 		var anyValue any