feat(sprint-5): Phase 7 — System test harness

- docker-compose.test.yml: full stack test profile with seed + playwright
- scripts/seed/init.sql: test data (admin, members, batches, distributions)
- scripts/seed/seed.sh: backend readiness validation script
- e2e/system-test.spec.ts: full user journey against real/mock stack
- package.json: test:e2e, test:system, test:all scripts
- scripts/README.md: system test documentation and usage instructions

docker-compose.test.yml

@@ -0,0 +1,46 @@
+# System test profile — runs full stack with seed data + Playwright
+# Usage: docker compose -f docker-compose.test.yml up --abort-on-container-exit
+include:
+  - docker-compose.yml
+
+services:
+  # Override db to include seed data
+  db:
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - ./scripts/seed/init.sql:/docker-entrypoint-initdb.d/99-seed.sql:ro
+
+  # Seed container: waits for backend health, then validates readiness
+  seed:
+    image: curlimages/curl:latest
+    container_name: cannamanage-seed
+    depends_on:
+      backend:
+        condition: service_healthy
+    entrypoint: /bin/sh
+    command: ["-c", "/seed/seed.sh"]
+    volumes:
+      - ./scripts/seed:/seed:ro
+
+  # Playwright system tests
+  playwright:
+    image: mcr.microsoft.com/playwright:v1.52.0-noble
+    container_name: cannamanage-playwright
+    working_dir: /app
+    depends_on:
+      seed:
+        condition: service_completed_successfully
+      frontend:
+        condition: service_started
+    environment:
+      BASE_URL: http://frontend:3000
+      CI: "true"
+    volumes:
+      - ./cannamanage-frontend:/app
+    command: >
+      sh -c "
+        echo 'Waiting for frontend to be ready...' &&
+        timeout 60 sh -c 'until wget -q -O /dev/null http://frontend:3000 2>/dev/null; do sleep 2; done' &&
+        echo 'Frontend ready — running system tests...' &&
+        npx playwright test e2e/system-test.spec.ts --reporter=list
+      "