refactor(db): streamline model imports and remove unused model exports

- Removed the export of models from the database connection module to simplify the structure.
- Updated various files to import models directly from the new centralized models module.
- Ensured consistency across the codebase by replacing mongoose model references with the new import paths.

api/server/controllers/AuthController.js

@@ -13,8 +13,8 @@ const {
 const { getOpenIdConfig } = require('~/strategies');
 const { isEnabled } = require('~/server/utils');
 
-const Session = mongoose.models.Session;
-const User = mongoose.models.User;
+const Session = require('~/db/models').Session;
+const User = require('~/db/models').User;
 
 const registrationController = async (req, res) => {
   try {

api/server/controllers/Balance.js

@@ -1,6 +1,6 @@
 const mongoose = require('mongoose');
 
-const Balance = mongoose.models.Balance;
+const Balance = require('~/db/models').Balance;
 
 async function balanceController(req, res) {
   const balanceData = await Balance.findOne(

api/server/controllers/TwoFactorController.js

@@ -10,7 +10,7 @@ const {
 const { encryptV3 } = require('~/server/utils/crypto');
 const safeAppTitle = (process.env.APP_TITLE || 'LibreChat').replace(/\s+/g, '');
 
-const User = mongoose.models.User;
+const User = require('~/db/models').User;
 
 /**
  * Enable 2FA for the user by generating a new TOTP secret and backup codes.

api/server/controllers/UserController.js

@@ -15,10 +15,10 @@ const { processDeleteRequest } = require('~/server/services/Files/process');
 const { deleteAllSharedLinks } = require('~/models/Share');
 const { deleteToolCalls } = require('~/models/ToolCall');
 
-const Transaction = mongoose.models.Transaction;
-const Session = mongoose.models.Session;
-const Balance = mongoose.models.Balance;
-const User = mongoose.models.User;
+const Transaction = require('~/db/models').Transaction;
+const Session = require('~/db/models').Session;
+const Balance = require('~/db/models').Balance;
+const User = require('~/db/models').User;
 
 const getUserController = async (req, res) => {
   /** @type {MongoUser} */

api/server/controllers/auth/TwoFactorAuthController.js

@@ -8,7 +8,7 @@ const {
 const { setAuthTokens } = require('~/server/services/AuthService');
 const { logger } = require('@librechat/data-schemas');
 
-const User = mongoose.models.User;
+const User = require('~/db/models').User;
 
 /**
  * Verifies the 2FA code during login using a temporary token.