enh: WHISPER_COMPUTE_TYPE env var

backend/open_webui/config.py

@@ -3675,6 +3675,7 @@ WHISPER_MODEL = PersistentConfig(
     os.getenv("WHISPER_MODEL", "base"),
 )
 
+WHISPER_COMPUTE_TYPE = os.getenv("WHISPER_COMPUTE_TYPE", "int8")
 WHISPER_MODEL_DIR = os.getenv("WHISPER_MODEL_DIR", f"{CACHE_DIR}/whisper/models")
 WHISPER_MODEL_AUTO_UPDATE = (
     not OFFLINE_MODE