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/models/Role.spec.js

@@ -9,7 +9,7 @@ const {
 const { getRoleByName, updateAccessPermissions, initializeRoles } = require('~/models/Role');
 const getLogStores = require('~/cache/getLogStores');
 
-const Role = mongoose.models.Role;
+const Role = require('~/db/models').Role;
 
 // Mock the cache
 jest.mock('~/cache/getLogStores', () =>