Default to HF free embedding (huggingface); require OPENAI_API_KEY only when using openai

Switch to Docker SDK: Fix Gradio API issue and use Docker for stability

Add Weaviate index builder Gradio app

方案 A: 预构建索引 Dataset，启动时直接下载免 embedding

Add retrieve API for Clare integration (api_name=retrieve)

Use Retriever instead of QueryEngine for HF embedding (fix Settings.llm import)

Add free Hugging Face embedding option (EMBEDDING_PROVIDER=huggingface)

Use HfApi + hf_hub_download instead of snapshot_download

Improve dataset snapshot download robustness

Use dataset-backed GENAI COURSES and build vector index