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/Token.js

@@ -1,7 +1,7 @@
 const mongoose = require('mongoose');
 const { encryptV2 } = require('~/server/utils/crypto');
 
-const Token = mongoose.models.Token;
+const Token = require('~/db/models').Token;
 
 /**
  * Handles the OAuth token by creating or updating the token.