feat: add docker-compose for PostgreSQL and initial EF Core migration

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  nexusrmm-postgres:
+    image: postgres:17
+    container_name: nexusrmm-postgres
+    environment:
+      POSTGRES_DB: nexusrmm
+      POSTGRES_USER: nexusrmm
+      POSTGRES_PASSWORD: nexusrmm_dev
+    ports:
+      - "5433:5432"
+    volumes:
+      - nexusrmm_pgdata:/var/lib/postgresql/data
+    restart: unless-stopped
+
+volumes:
+  nexusrmm_pgdata:
+    name: nexusrmm_pgdata