Fix code scanning alert no. 3: Database query built from user-controlled sources

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: 6TELOIV

api/accounts.mjs

@@ -128,8 +128,8 @@ router.get("/user", async (req, res, next) => {
                 username = username.substring(1);
             }
             const user = await db.collection("users").findOne({
-                username: username,
-                discriminator: discriminator,
+                username: { $eq: username },
+                discriminator: { $eq: discriminator },
             });
 
             if (user === null) {