feat: consolidate backend and docker-compose setup

backend/db/migrations/004_create_customer_master.sql

@@ -0,0 +1,12 @@
+-- Migration: 004_create_customer_master
+-- Description: Create customers table and seed the initial customer entry
+
+CREATE TABLE IF NOT EXISTS customers (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(255) UNIQUE NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+INSERT INTO customers (name)
+VALUES ('PT.PRIMAFOOD INTERNATIONAL, JL. ANCOL BARAT VIII/1, ANCOL, PADEMANGAN, JAKARTA UTARA, 14430')
+ON CONFLICT (name) DO NOTHING;