[Rebase] Align vLLM-Omni with vLLM v0.31.0 (#8459)

Signed-off-by: tzhouam <tzhouam@connect.ust.hk>

docker/Dockerfile.ci.dockerignore

@@ -1,6 +1,6 @@
 # NOTE: this is largely taken from vLLM
 
-# Exclude .git for CI builds — version is set via SETUPTOOLS_SCM_PRETEND_VERSION
+# Exclude .git for CI builds — version is set via VLLM_OMNI_VERSION_OVERRIDE
 .git
 .venv
 /build