updates to M3 module

Modules/M3/README.md

@@ -0,0 +1,29 @@
+# M3 Core Module
+
+M3 functionality migrated from the standalone M3 application into Core.
+
+## Database
+
+The module uses Core's PostgreSQL connection by default. Override with `M3_DB_CONNECTION` if M3 data uses another configured PostgreSQL connection.
+
+No DB2, ODBC, IBM i Access, or `zendtech/ibmitoolkit` dependency is required.
+
+Legacy IBM i program-call requests are captured by `PostgresProgramBridge` in `m3_program_requests`, allowing a PostgreSQL-native worker/integration to process them independently of HTTP requests.
+
+## Optional paths
+
+- `M3_LABELS_PATH`
+- `M3_CLOSING_ORDERS_PATH`
+
+Both default beneath `storage/app/m3`.
+
+## After replacing the module
+
+```bash
+composer dump-autoload
+php artisan optimize:clear
+php artisan migrate
+php artisan route:list --path=m3
+```
+
+Health check: `/m3/health`.