更新登录逻辑，等待数据库进一步完善

accounts/crypto.py

@@ -0,0 +1,20 @@
+import hashlib
+import hmac
+
+
+def salt_for_username(username: str) -> bytes:
+    """Derive a per-username salt using SHA-256(username).
+
+    The salt is deterministic for a given username and does not require storage.
+    """
+    return hashlib.sha256(username.encode('utf-8')).digest()
+
+
+def derive_password(password_plain: str, salt: bytes, iterations: int = 100_000, dklen: int = 32) -> bytes:
+    """PBKDF2-SHA256 derive a fixed-length secret from a plaintext password and salt."""
+    return hashlib.pbkdf2_hmac('sha256', password_plain.encode('utf-8'), salt, iterations, dklen=dklen)
+
+
+def hmac_sha256(key: bytes, message: bytes) -> bytes:
+    """Compute HMAC-SHA256 signature for the given message using key bytes."""
+    return hmac.new(key, message, hashlib.sha256).digest()