get keep alive from env (#9039)

### What problem does this PR solve?

get keepalive from env

### Type of change

- [x] Refactoring

rag/llm/cv_model.py

         self.client = Client(host=kwargs["base_url"])
         self.model_name = model_name
         self.lang = lang
+        self.keep_alive = kwargs.get("ollama_keep_alive", int(os.environ.get("OLLAMA_KEEP_ALIVE", -1)))
 
     def describe(self, image):
         prompt = self.prompt("")
                 model=self.model_name,
                 messages=history,
                 options=options,
-                keep_alive=-1,
+                keep_alive=self.keep_alive,
             )
 
             ans = response["message"]["content"].strip()
                 messages=history,
                 stream=True,
                 options=options,
-                keep_alive=-1,
+                keep_alive=self.keep_alive,
             )
             for resp in response:
                 if resp["done"]:

rag/llm/embedding_model.py

     def __init__(self, key, model_name, **kwargs):
         self.client = Client(host=kwargs["base_url"]) if not key or key == "x" else Client(host=kwargs["base_url"], headers={"Authorization": f"Bearer {key}"})
         self.model_name = model_name
+        self.keep_alive = kwargs.get("ollama_keep_alive", int(os.environ.get("OLLAMA_KEEP_ALIVE", -1)))
 
     def encode(self, texts: list):
         arr = []
             # remove special tokens if they exist
             for token in OllamaEmbed._special_tokens:
                 txt = txt.replace(token, "")
-            res = self.client.embeddings(prompt=txt, model=self.model_name, options={"use_mmap": True}, keep_alive=-1)
+            res = self.client.embeddings(prompt=txt, model=self.model_name, options={"use_mmap": True}, keep_alive=self.keep_alive)
             try:
                 arr.append(res["embedding"])
             except Exception as _e:
         # remove special tokens if they exist
         for token in OllamaEmbed._special_tokens:
             text = text.replace(token, "")
-        res = self.client.embeddings(prompt=text, model=self.model_name, options={"use_mmap": True}, keep_alive=-1)
+        res = self.client.embeddings(prompt=text, model=self.model_name, options={"use_mmap": True}, keep_alive=self.keep_alive)
         try:
             return np.array(res["embedding"]), 128
         except Exception as _e: