chore(backend): add ruff configuration

pyproject.toml

@@ -31,10 +31,9 @@ redis = [
 
 [dependency-groups]
 dev = [
-    "black>=24.0.0",
-    "flake8>=7.0.0",
     "pytest>=8.0.0",
     "pytest-asyncio>=0.24.0",
+    "ruff>=0.15.12",
 ]
 
 [build-system]
@@ -45,3 +44,14 @@ build-backend = "setuptools.build_meta"
 where = ["apps"]
 include = ["backend*"]
 namespaces = true
+
+[tool.ruff]
+line-length = 100
+target-version = "py39"
+src = ["apps", "tests"]
+
+[tool.ruff.lint]
+select = ["E9", "F821"]
+
+[tool.ruff.lint.per-file-ignores]
+"apps/backend/scripts/*.py" = ["E402"]