fix: allow WebTerminal init without OCR API key (openai>=2.40 requires key)

modules/ocr_client.py

@@ -26,6 +26,8 @@ class OCRClient:
 
         # httpx 0.28 起不再支持 proxies 参数，显式传入 http_client 以避免默认封装报错
         self.http_client = httpx.Client()
+        self.client = None
+        if OCR_API_KEY:
             self.client = OpenAI(
                 api_key=OCR_API_KEY,
                 base_url=base_url or None,
@@ -58,7 +60,7 @@ class OCRClient:
 
         if not prompt or not str(prompt).strip():
             return {"success": False, "error": "prompt 不能为空", "warnings": warnings}
-        if not OCR_API_KEY or not OCR_API_BASE_URL or not self.model:
+        if not self.client or not OCR_API_KEY or not OCR_API_BASE_URL or not self.model:
             return {"success": False, "error": "VLM 配置缺失，请设置 OCR_API_BASE_URL / OCR_API_KEY / OCR_MODEL_ID", "warnings": warnings}
 
         try: