[doc] upgrade NPU A2/A3 Docker images

[UsernameFull]

Summary

Upgrade the Ascend NPU A2/A3 Docker images and synchronize all related documentation.

Changes

• Upgrade the base images from CANN 9.0.0 / Python 3.11 to CANN 9.1.0 / Python 3.12.
• Upgrade core dependencies:
  • PyTorch: 2.9.0 → 2.10.0
  • torch-npu: 2.10.0.post4
  • vLLM: 0.18.0 → 0.23.0
  • vLLM-Ascend: 0.18.0 → 0.23.0rc1
• Initialize vLLM-Ascend submodules and use the Ascend package mirror.
• Exclude gem-llm from the common requirements when building NPU images.
• Update A2/A3 Docker image tags to include CANN, torch-npu, hardware, Ubuntu, and Python versions.
• Update NPU device mounting, ulimit, and environment verification instructions.
• Synchronize English and Chinese documentation, including:
  • OVERVIEW.md
  • Docker usage guide
  • Ascend usage guide
  • RLVR and example guides
  • FAQ and environment configuration
• Remove unrelated Ascend 950 content from the A2/A3 Docker usage guide.