Fix CI: clean stale DB before e2e tests, fix reminder selector

- Clean previous run's DB/WAL/SHM files and kill stale processes
  before starting backend, preventing test data contamination
- reminders-flow: use parents('.reminder-card') to find .remove-btn

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/test.yml

@@ -23,7 +23,14 @@ jobs:
 
       - name: E2E tests
         run: |
-          # Start backend
+          # Clean stale data from previous runs
+          rm -f /tmp/ci_planner_test.db /tmp/ci_planner_test.db-wal /tmp/ci_planner_test.db-shm
+          rm -rf /tmp/ci_planner_data
+          pkill -f "uvicorn backend" || true
+          pkill -f "node.*vite" || true
+          sleep 1
+
+          # Start backend with fresh DB
           DB_PATH=/tmp/ci_planner_test.db FRONTEND_DIR=/dev/null DATA_DIR=/tmp/ci_planner_data \
             /tmp/ci-venv/bin/uvicorn backend.main:app --port 8000 &