chore: 添加 rank-bm25 依赖（混合检索用）

uv.lock

@@ -1104,6 +1104,7 @@ dependencies = [
     { name = "markdown-it-py" },
     { name = "python-dotenv" },
     { name = "pyyaml" },
+    { name = "rank-bm25" },
     { name = "sentence-transformers" },
     { name = "typer" },
     { name = "uvicorn", extra = ["standard"] },
@@ -1150,6 +1151,7 @@ requires-dist = [
     { name = "pytest-cov", marker = "extra == 'dev'", specifier = ">=5.0" },
     { name = "python-dotenv", specifier = ">=1.2.2" },
     { name = "pyyaml", specifier = ">=6.0" },
+    { name = "rank-bm25", specifier = ">=0.2.2" },
     { name = "requests", marker = "extra == 'all'", specifier = ">=2.31.0" },
     { name = "ruff", marker = "extra == 'dev'", specifier = ">=0.8.0" },
     { name = "sentence-transformers", specifier = ">=3.0.0" },
@@ -2158,6 +2160,18 @@ wheels = [
     { url = "https://pypi.tuna.tsinghua.edu.cn/packages/f1/12/de94a39c2ef588c7e6455cfbe7343d3b2dc9d6b6b2f40c4c6565744c873d/pyyaml-6.0.3-cp314-cp314t-win_arm64.whl", hash = "sha256:ebc55a14a21cb14062aa4162f906cd962b28e2e9ea38f9b4391244cd8de4ae0b", size = 149341, upload-time = "2025-09-25T21:32:56.828Z" },
 ]
 
+[[package]]
+name = "rank-bm25"
+version = "0.2.2"
+source = { registry = "https://pypi.tuna.tsinghua.edu.cn/simple/" }
+dependencies = [
+    { name = "numpy" },
+]
+sdist = { url = "https://pypi.tuna.tsinghua.edu.cn/packages/fc/0a/f9579384aa017d8b4c15613f86954b92a95a93d641cc849182467cf0bb3b/rank_bm25-0.2.2.tar.gz", hash = "sha256:096ccef76f8188563419aaf384a02f0ea459503fdf77901378d4fd9d87e5e51d", size = 8347, upload-time = "2022-02-16T12:10:52.196Z" }
+wheels = [
+    { url = "https://pypi.tuna.tsinghua.edu.cn/packages/2a/21/f691fb2613100a62b3fa91e9988c991e9ca5b89ea31c0d3152a3210344f9/rank_bm25-0.2.2-py3-none-any.whl", hash = "sha256:7bd4a95571adadfc271746fa146a4bcfd89c0cf731e49c3d1ad863290adbe8ae", size = 8584, upload-time = "2022-02-16T12:10:50.626Z" },
+]
+
 [[package]]
 name = "referencing"
 version = "0.37.0"