Switch backend to wait for SQL Server and use direct INSERTs

Replace stored procedure calls with inline INSERT statements and
SCOPE_IDENTITY()
Add netcat for readiness check in new entrypoint.sh
Introduce dedicated SQL Server and init-db services in docker-compose

db/init.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+# init.sh - Initialize the SQL Server database with the schema and sample data.
+# This script is intended to be run inside the SQL Server container (or from the host
+# with sqlcmd reachable). It executes the init.sql script located in the same
+# directory.
+
+set -euo pipefail
+
+# Default connection settings – can be overridden via environment variables
+: "${DB_SERVER:=localhost}"
+: "${DB_USER:=sa}"
+: "${DB_PASSWORD:=YourStrong!Passw0rd}"
+: "${DB_NAME:=CustomerDB}"
+: "${SQLCMD_PATH:=sqlcmd}"   # Path to the sqlcmd executable
+
+# Path to the init script (relative to this script's location)
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+INIT_SQL="${SCRIPT_DIR}/init.sql"
+
+if [[ ! -f "${INIT_SQL}" ]]; then
+    echo "❌ init.sql not found at ${INIT_SQL}"
+    exit 1
+fi
+
+echo "🚀 Running database initialization..."
+"${SQLCMD_PATH}" -S "${DB_SERVER}" -U "${DB_USER}" -P "${DB_PASSWORD}" -d "master" -Q "IF DB_ID(N'${DB_NAME}') IS NULL CREATE DATABASE ${DB_NAME};"
+
+# Run the init script against the newly created database
+"${SQLCMD_PATH}" -S "${DB_SERVER}" -U "${DB_USER}" -P "${DB_PASSWORD}" -d "${DB_NAME}" -i "${INIT_SQL}"
+
+echo "✅ Database ${DB_NAME} initialized successfully."