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/strategies/appleStrategy.test.js

@@ -7,7 +7,7 @@ const { createSocialUser, handleExistingUser } = require('./process');
 const { isEnabled } = require('~/server/utils');
 const socialLogin = require('./socialLogin');
 
-const User = mongoose.models.User;
+const User = require('~/db/models').User;
 
 // Mocking external dependencies
 jest.mock('jsonwebtoken');