Improve feed sorting, groups discovery, and daily recommended UX

[sdk-kr]

Summary

• add sort options to the feed and support server-side ranking by latest, comments, and views
• improve groups discovery with activity filters, sorting, and weekly/subscriber metrics
• restyle daily recommended lists to match explore density and add explore board filtering

Validation

• pnpm build
• pnpm exec prettier --check src/lib/server/new-posts.ts src/routes/feed/+page.server.ts src/routes/feed/+page.svelte src/routes/groups/+page.server.ts src/routes/groups/+page.svelte src/lib/components/ui/post-card/post-card.svelte src/lib/components/features/daily-recommended/comment-card.svelte src/lib/components/features/daily-recommended/daily-recommended-page.svelte src/routes/explore/+page.svelte src/lib/components/features/my/my-nav.svelte

Notes

• repo-wide lint and svelte-check still report many pre-existing issues outside this change set