docs: sync all documentation with current codebase

- remove GenerationRequest and generate_with_request references (class deleted)
- document cuda>flash>torch default priority and FlashAttnBackend
- add ASTR_BACKEND env var to backend docs, TorchNativeBackend (default) → (fallback)
- fix JsonlStore transform routing → DatasetFactory ownership
- fix CudaBackend fallback chain description (FlashAttn → TorchNative)
- add FlashAttnBackend to architecture strategy table
- add router_stats to DecoderOutput/FFNOutput TypedDict diagrams
- add decode_o_part/ml_part/decode_out to KVCache diagram
- add --append_eos/--no-append_eos to IFD evaluation parameter table
- update get-started CUDA kernel note (no longer requires explicit attn_backend activation)
- fix python -m scripts.tools.server (no __init__.py) → direct script call

docs/README-zh-CN.md

@@ -187,7 +187,7 @@ docker run --gpus all -it astrai:latest
 
 # 运行推理服务
 docker run --gpus all -p 8000:8000 astrai:latest \
-  python -m scripts.tools.server --port 8000 --device cuda
+  python scripts/tools/server.py --port 8000 --device cuda
 
 # 挂载数据卷
 docker run --gpus all -v /path/to/data:/data -it astrai:latest