test(e2e): add Playwright E2E tests for auth, tasks, and shifts

Tasks 26-28: Comprehensive E2E test suite covering:
- Auth flow with Keycloak OIDC (6 tests)
- Task management lifecycle (10 tests)
- Shift sign-up and capacity enforcement (4 tests)

Total: 20 E2E tests (auth + tasks + shifts + smoke)

Tests require Docker Compose stack to run, but all compile successfully.

.sisyphus/evidence/task-26-test-status.txt

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+# Task 26: Playwright E2E Tests - Test Status Report
+
+## Test File Created
+✅ frontend/e2e/auth.spec.ts (244 lines)
+
+## Tests Discovered
+✅ 6 comprehensive E2E tests for authentication flow:
+1. Scenario 1: Full auth flow E2E - redirect → Keycloak → club picker → dashboard
+2. Scenario 2: Club switching refreshes data  
+3. Scenario 3: Logout flow - clears session and blocks protected routes
+4. Unauthenticated user blocked from protected routes
+5. Single-club user bypasses club picker
+6. Keycloak login with invalid credentials fails
+
+## TypeScript Compilation
+✅ No errors - all tests compile successfully
+
+## Test Execution Status
+⚠️ BLOCKED: Tests cannot fully run due to environment configuration
+
+### Blocking Issues:
+1. **AUTH_SECRET not configured** - Auth.js requires AUTH_SECRET in .env
+2. **Docker services not running** - Keycloak, PostgreSQL unavailable
+3. **Keycloak realm not seeded** - Test users not available
+
+### Partial Test Results:
+- Tests started and Next.js dev server launched
+- Playwright successfully interacts with pages
+- Auth middleware triggered (MissingSecret error proves middleware works)
+- One test attempted redirect flow (got to /login but no callbackUrl query param)
+
+## What Works:
+✅ Test syntax and structure
+✅ Playwright configuration  
+✅ Browser automation setup
+✅ Test discovery and compilation
+✅ Next.js integration (webServer starts)
+✅ Middleware execution (detected missing secret)
+
+## What's Needed for Full Execution:
+1. Start Docker Compose stack: `docker compose up -d`
+2. Add AUTH_SECRET to frontend/.env: `AUTH_SECRET=<random-string>`
+3. Add Keycloak config to .env:
+   - KEYCLOAK_CLIENT_ID=workclub-app
+   - KEYCLOAK_CLIENT_SECRET=<leave empty for public client>
+   - KEYCLOAK_ISSUER=http://localhost:8080/realms/workclub
+4. Verify Keycloak realm imported with test users
+5. Run: `cd frontend && bunx playwright test e2e/auth.spec.ts`
+
+## Evidence Files:
+- frontend/e2e/auth.spec.ts — Complete test implementation
+- .sisyphus/evidence/task-26-test-status.txt — This report
+- .sisyphus/evidence/task-26-test-execution.txt — Partial test run output
+
+## Verification Command (when environment ready):
+```bash
+cd frontend
+bunx playwright test e2e/auth.spec.ts --reporter=list
+```
+
+Expected result: 6/6 tests passing, screenshots saved to .sisyphus/evidence/