Dev: Fix useExhaustiveDependencies — HFI Calculator

[conbrad]

Describe the task
Remove biome-ignore lint/correctness/useExhaustiveDependencies comments and properly fix dep arrays in the HFI Calculator page and station admin modal.

Acceptance Criteria

• Remove biome-ignore comments from apps/wps-web/src/features/hfiCalculator/pages/HfiCalculatorPage.tsx (7 effects: mount fetch, updatedPlanningAreaId ×2, selectedFireCentre, dateRange, fireCentres, stationsUpdateLoading)
• Remove biome-ignore comments from apps/wps-web/src/features/hfiCalculator/components/stationAdmin/ManageStationsModal.tsx (line 85)
• yarn biome lint passes with zero useExhaustiveDependencies errors on both files
• Page loads and fetches stations on mount
• Switching fire centres shows loading indicator and fetches the correct date range
• No repeated API calls visible in the network tab

Additional context

• CAUTION: a previous attempt here introduced an API flood loop and a lost loading indicator when switching fire centres. The mount effect and the fireCentres/selectedFireCentre interaction are particularly sensitive.
• Use useRef to read current values without subscribing if needed to break dep cycles.