Uploads two different avatars in sequence and verifies the header
avatar src changes after the second upload. This confirms both the
backend cache (via DelPrefix) and the frontend cache are properly
invalidated when a new avatar is uploaded.
- Re-enable 16 previously skipped Playwright E2E tests that now pass
- Fix test setup issues that were causing flakiness
## Changes
- **task/task.spec.ts** (8 tests): kanban navigation, description
editing, assignees, labels, due dates
- **task/overview.spec.ts** (4 tests): task ordering, due date handling
- **user/settings.spec.ts** (2 tests): avatar upload, name update
- **user/login.spec.ts** (2 tests): bad password error, redirect after
login
## Key fixes
- Kanban view tests now properly create `TaskBucket` entries so tasks
appear in the kanban board
- Avatar upload test uses the API directly to avoid `canvas.toBlob()`
issues in headless browser environments
- Login redirect test no longer uses the shared `login()` helper that
expected redirect to `/`
kolaente