[chore]: switch deploy schedule from daily to weekly

[chloe41427]

Summary

• Changes the scheduled deploy cron in .github/workflows/deploy.yml from daily (0 0 * * *) to weekly on Sundays at midnight (0 0 * * 0).
• The site is still rebuilt on every push to main and via workflow_dispatch, so any content updates continue to deploy immediately — this only reduces redundant scheduled rebuilds when nothing has changed.

Test plan

• CI passes on the PR
• After merge, confirm the next scheduled run lands on a Sunday at 00:00 UTC

[chloe41427]

No longer needed — the daily schedule is working fine and we've decided to keep it as-is.