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/middleware/checkBan.js

@@ -8,7 +8,7 @@ const keyvMongo = require('~/cache/keyvMongo');
 const denyRequest = require('./denyRequest');
 const { getLogStores } = require('~/cache');
 
-const User = mongoose.models.User;
+const User = require('~/db/models').User;
 
 const banCache = new Keyv({ store: keyvMongo, namespace: ViolationTypes.BAN, ttl: 0 });
 const message = 'Your account has been temporarily banned due to violations of our service.';