feat(trainer): add GitHub activity heatmap, 4-option quiz mode, active typing, and duplicate checks

app/auth.py

@@ -108,9 +108,31 @@ def delete_session(token: str):
     with get_db() as conn:
         conn.execute("DELETE FROM sessions WHERE token = ?", (token,))
 
+def change_user_password(user_id: int, old_password: str, new_password: str) -> tuple[bool, str]:
+    """Changes password for the specified user after verifying old password."""
+    if not new_password or len(new_password) < 6:
+        return False, "Новый пароль должен содержать минимум 6 символов"
+    with get_db() as conn:
+        row = conn.execute(
+            "SELECT password_hash, salt FROM users WHERE id = ?",
+            (user_id,)
+        ).fetchone()
+        if not row:
+            return False, "Пользователь не найден"
+        if not verify_password(old_password, row["password_hash"], row["salt"]):
+            return False, "Неверный текущий пароль"
+        pwd_hash, salt = hash_password(new_password)
+        conn.execute(
+            "UPDATE users SET password_hash = ?, salt = ? WHERE id = ?",
+            (pwd_hash, salt, user_id)
+        )
+        return True, "Пароль успешно изменён"
+
+
 def ensure_admin_user():
     """Ensures at least one user exists; creates default admin from config if table empty."""
     with get_db() as conn:
         count = conn.execute("SELECT COUNT(*) FROM users").fetchone()[0]
         if count == 0 and config.ADMIN_PASSWORD:
             create_user(config.ADMIN_USERNAME, config.ADMIN_PASSWORD)
+