/claim #1162

Summary

This adds an optional historical date mode for the map/sites view so users can inspect past heat-stress conditions instead of always seeing current/latest values.

What changed

• Added optional at filter support in GET /sites.
  • FilterSiteDto now accepts at (ISO date)
  • SitesService.find passes at through to collection data resolution
• Extended collection-data mapping to support historical snapshots.
  • For historical mode, data is sourced from daily_data (latest row up to selected day)
  • Mapped to existing frontend marker fields (dhw, satelliteTemperature, tempAlert, tempWeeklyAlert)
• Added map UI control to choose/clear a historical date.
  • Floating calendar control on HomeMap
  • URL query sync via ?at=YYYY-MM-DD
• Updated sites request flow to refetch when historical date changes.
  • sitesRequest now tracks requestedAt context
  • Search component aligns prefetch with current URL date context so historical view is not overwritten

Why this is safe

• Default behavior remains unchanged when at is not provided.
• Historical mode only changes collection-data source path used for map/site cards.
• Existing filters and route flow remain intact.

Validation

• YARN_IGNORE_ENGINES=1 corepack yarn workspace api test src/utils/collections.utils.test.ts
• YARN_IGNORE_ENGINES=1 corepack yarn workspace website test src/services/siteServices.test.ts
• YARN_IGNORE_ENGINES=1 corepack yarn workspace api eslint src/sites/dto/filter-site.dto.ts src/sites/sites.service.ts src/utils/collections.utils.ts src/utils/collections.utils.test.ts
• YARN_IGNORE_ENGINES=1 corepack yarn workspace website eslint --ext .ts,.tsx src/routes/HomeMap/index.tsx src/routes/HomeMap/Map/index.tsx src/common/Search/index.tsx src/store/Sites/sitesListSlice.ts src/services/siteServices.ts src/services/siteServices.test.ts