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

backend/entrypoint.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env sh
+
+# entrypoint.sh – wait for the SQL Server container to become ready
+# before starting the Go backend binary.
+
+set -e
+
+# Default environment variables (can be overridden in docker-compose)
+: "${DB_SERVER:=sql}"
+: "${DB_USER:=sa}"
+: "${DB_PASSWORD:=Ou812@12!@}"
+
+# Wait until netcat can successfully connect to the SQL Server port
+while ! nc -z "$DB_SERVER" 1433; do
+    echo "⏳ Waiting for SQL Server at $DB_SERVER:1433..."
+    sleep 1
+done
+# Add a short pause after the port is open to let SQL Server finish startup
+sleep 5
+# Add a short pause after the port is open to let SQL Server finish startup
+sleep 2
+
+echo "✅ SQL Server is ready. Starting backend."
+exec ./main