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

cannamanage-frontend/e2e/integration/README.md

@@ -0,0 +1,22 @@
+# Integration Tests
+
+Full-stack integration tests that run against a real backend + database.
+
+## Running locally
+
+```bash
+docker compose -f docker-compose.test.yml -f docker-compose.test.local.yml up --build
+```
+
+## Running in CI
+
+```bash
+docker compose -f docker-compose.test.yml up --build --abort-on-container-exit
+```
+
+## Test Structure
+
+- Each spec file tests one page/feature
+- Tests use `data-testid` selectors from `../selectors.ts`
+- Expected values come from `../seed-constants.ts`
+- DB is reset before each test via `ApiClient.resetDb()`