[CICD]: Add 910C image and unified model management

[HermiaHuan]

Summary

• Add an Ascend 910C Docker image based on quay.io/ascend/vllm-ascend:v0.20.2rc1-a3
• Standardize host model paths under /data/models/
• Store Qwen models under /data/models/Qwen/
• Download Qwen3-0.6B through https://hf-mirror.com
• Add Ascend 910C serving and chat E2E tests
• Use manually triggered Ascend CI to avoid unnecessarily occupying scarce NPU runners

Manual validation

Validated on bm-jn-zs-bj2-910C-64G-10-115:

• Branch: dev-hr-ascend
• Commit: ecd3eb6
• Image: harbor.baai.ac.cn/flagscale/vllm-plugin-fl:ascend-vllm0.20.2-a3-ci
• Image digest: sha256:5062ac23b8b8247e5b4faa5d2c61b7b8e82e46a9ae7c55fe15c5cdbe3533f4b7
• Model: /data/models/Qwen/Qwen3-0.6B
• NumPy: 1.26.4
• Pytest: 2 passed
• Result: Overall: PASSED