Chore: unify Ruff config and enable async checks (ASYNC, TRIO) (#6351)

### What problem does this PR solve?

Unify Ruff config and enable async checks (ASYNC, TRIO)

### Type of change

- [x] CI/CD or tooling improvement

.github/workflows/tests.yml

         uses: astral-sh/ruff-action@v2
         with:
           version: ">=0.8.2"
-          args: "check --ignore E402"
+          args: "check"
 
       - name: Build ragflow:nightly-slim
         run: |

pyproject.toml

 
 [[tool.uv.index]]
 url = "https://mirrors.aliyun.com/pypi/simple"
+
+[tool.ruff]
+line-length = 200
+exclude = [
+    ".venv",
+    "rag/svr/discord_svr.py",
+]
+
+[tool.ruff.lint]
+extend-select = ["ASYNC", "ASYNC1"]
+ignore = ["E402"]