chore: add mise format and lint tasks (ruff + Biome)

Tools are pinned in mise.toml. ruff.toml points first-party detection at backend/, since the frontend's src/auth, src/books and src/notes otherwise get matched as first-party. biome.json uses spaces to match the existing Prettier-style formatting. Also combines a nested with in test_passwords.py (ruff SIM117).

backend/tests/test_passwords.py

@@ -8,7 +8,6 @@ from unittest import mock
 from auth import ITERATIONS, hash_password, load_pepper, needs_rehash, verify_password
 
 PEPPER = b"p" * 32
-# Independently computed: HMAC-SHA256(PEPPER, password) -> PBKDF2-SHA256, 1000 iterations, 16 zero-byte salt.
 KNOWN_ANSWER = "pbkdf2_sha256$1000$AAAAAAAAAAAAAAAAAAAAAA==$9ZLLEusnEPU3Km8h+vnd4ue9fw7rHdm4QwuBX5ozynE="
 
 
@@ -41,9 +40,11 @@ class PasswordHashTests(unittest.TestCase):
 
 class PepperTests(unittest.TestCase):
     def test_env_pepper_must_be_long_enough(self):
-        with mock.patch.dict(os.environ, {"PASSWORD_PEPPER": "short"}):
-            with self.assertRaisesRegex(RuntimeError, "at least 32 characters"):
-                load_pepper(Path("/nonexistent"))
+        with (
+            mock.patch.dict(os.environ, {"PASSWORD_PEPPER": "short"}),
+            self.assertRaisesRegex(RuntimeError, "at least 32 characters"),
+        ):
+            load_pepper(Path("/nonexistent"))
 
     def test_env_pepper_is_used_when_set(self):
         with mock.patch.dict(os.environ, {"PASSWORD_PEPPER": "e" * 40}):