Phase 1: Add SiliconFlow provider + DeepSeek-V4-Flash, optimize Dockerfile with Tsinghua mirrors

.env

@@ -1,5 +1,5 @@
-# Qihu-AIFlow 环境配置
-# 注：MYSQL_HOST/REDIS_HOST 由 Docker 环境变量传入，本地默认 localhost
+# Qihu-AIFlow Environment Configuration
+# Docker Compose uses environment variables directly, local dev uses .env
 
 MYSQL_PORT=3306
 MYSQL_USER=root
@@ -10,8 +10,13 @@ REDIS_PORT=6379
 REDIS_PASSWORD=pwd2026
 
 SECRET_KEY=aiflow-secret-key-change-in-production-2026
-APP_ACCESS_URL=https://bot.qihuyun.com
+APP_ACCESS_URL=http://210.16.161.218:12888
 DEBUG=false
 
-# 知识库文件存储目录
+# Knowledge file storage directory
 KNOWLEDGE_STORAGE_DIR=/data/share/project/data/knowledge
+
+# SiliconFlow API (default LLM provider)
+SILICONFLOW_API_KEY=sk-idsplzeccvmbtyqxcrbhaiwmkzwajmicliunkjkouivepaaz
+SILICONFLOW_BASE_URL=https://api.siliconflow.cn
+DEFAULT_MODEL=deepseek-ai/DeepSeek-V4-Flash