use cloud sql instance name

Author: stefanbobrowski

backend/db.js

@@ -2,10 +2,12 @@ const { Pool } = require('pg');
 
 const pool = new Pool({
   user: process.env.DB_USER,
-  host: process.env.DB_HOST,
+  // host: process.env.DB_HOST,
+  host: `/cloudsql/${process.env.INSTANCE_CONNECTION_NAME}`, // 👈 this is the socket path
   database: process.env.DB_NAME,
   password: process.env.DB_PASSWORD,
   port: process.env.DB_PORT,
+
   ssl: {
     rejectUnauthorized: false, // disables certificate validation for dev
   },