test(calendar): stabilize date-sensitive page fixtures

[h4yfans]

What

Stabilize the CalendarPage renderer fixtures so they follow the active local day instead of hard-coded April 2026 timestamps.

Why

All open tech-debt PRs are currently blocked by the same failing renderer test in calendar-page.test.tsx. The test data was anchored to stale fixed dates while CalendarPage derives its initial day view from the current date, so CI started failing once the calendar fixtures drifted out of sync with the runtime day.

How

Use a small local-date fixture helper in calendar-page.test.tsx.
Keep the day-view Memry items on the current local day.
Move the imported calendar event to the next local day so the month-view assertions still render both Memry and imported items without overflowing one cell.

Type

• feat — new feature
• fix — bug fix
• refactor — restructure without behavior change
• style — visual/UI only
• test — adding or updating tests
• chore — tooling, deps, config
• docs — documentation only
• ci — CI/CD changes

Test plan

• Unit tests added/updated
• Integration tests added/updated
• Manual testing (describe below)

pnpm exec vitest run --config config/vitest.config.ts src/renderer/src/components/calendar/calendar-page.test.tsx
pnpm lint

Checklist

• Self-reviewed the diff
• No hardcoded secrets or credentials
• Files stay under ~500 LOC
• Follows immutable data patterns