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/Dockerfile.playwright

@@ -0,0 +1,18 @@
+# IMPORTANT: Keep this version in sync with @playwright/test in package.json
+FROM mcr.microsoft.com/playwright:v1.60.0-noble
+
+WORKDIR /app
+
+# Copy package files for dependency installation
+COPY package.json pnpm-lock.yaml .npmrc ./
+
+# Install pnpm and project dependencies at build time
+RUN corepack enable && corepack prepare pnpm@latest --activate
+RUN pnpm install --frozen-lockfile
+
+# Copy playwright config and test infrastructure
+COPY playwright.config.ts tsconfig.json ./
+COPY e2e/ ./e2e/
+
+# Default command (overridden by docker-compose)
+CMD ["npx", "playwright", "test", "e2e/integration/", "--reporter=list"]