test: add full-stack Playwright integration test infrastructure

Sprint 12 Phase 2: Real integration tests with seed DB
- R__seed_test_data.sql (Flyway repeatable, 7 members, strains, batches, docs, board, events)
- TestResetController (profile-gated per-test DB reset)
- docker-compose.test.yml (self-contained, tmpfs Postgres)
- Dockerfile.playwright (v1.60.0, pre-installed deps)
- 13 integration spec files, 70+ test cases (@smoke + @full)
- seed-constants.ts, selectors.ts, api-client.ts test helpers

docker-compose.test.local.yml

@@ -0,0 +1,10 @@
+# Local dev override — replaces tmpfs with named volume for macOS compatibility
+# Usage: docker compose -f docker-compose.test.yml -f docker-compose.test.local.yml up --build
+services:
+  db:
+    tmpfs: !reset []
+    volumes:
+      - test-pgdata:/var/lib/postgresql/data
+
+volumes:
+  test-pgdata: