chore(backend): add black/isort/flake8 + pre-commit

.pre-commit-config.yaml

@@ -0,0 +1,28 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+      - id: check-yaml
+      - id: check-added-large-files
+
+  - repo: https://github.com/psf/black
+    rev: 24.10.0
+    hooks:
+      - id: black
+        language_version: python3
+        files: ^backend/.*\.py$
+
+  - repo: https://github.com/PyCQA/isort
+    rev: 5.13.2
+    hooks:
+      - id: isort
+        files: ^backend/.*\.py$
+
+  - repo: https://github.com/PyCQA/flake8
+    rev: 7.1.1
+    hooks:
+      - id: flake8
+        files: ^backend/.*\.py$
+        args: [--config=backend/.flake8]