refactor(db): replace connectDb import paths and introduce new connect module

- Updated import paths for connectDb across various files to use the new centralized connect module.
- Removed the old connectDb file to streamline the database connection logic.
- Ensured all tests and models reference the new connection method for consistency.

api/models/spendTokens.js

@@ -1,5 +1,5 @@
 const { logger } = require('~/config');
-const db = require('~/lib/db/connectDb');
+const db = require('db/connect');
 const { createTransaction, createStructuredTransaction } = require('./Transaction');
 /**
  * Creates up to two transactions to record the spending of tokens.