Move pace math out of the dashboard utility bulk

Pace-adjusted high calculations were embedded in dashboard-utils alongside chart, profile, and modal helpers. This moves the pure pace model and reusable HM time helpers into focused modules while keeping dashboard-utils re-export compatibility for older callers.

Constraint: Preserve existing pace wording, thresholds, and calculation output.

Rejected: Split all remaining dashboard-utils helpers at once | model/chart/modal helpers have wider call surfaces and should move in separate reversible passes.

Confidence: high

Scope-risk: narrow

Reversibility: clean

Tested: TypeScript diagnostics for pace-utils, time-utils, dashboard-utils, and FutureForecastModal

Tested: npm run build

Not-tested: Bundle analyzer size comparison.

frontend/components/dashboard/FutureForecastModal.tsx

@@ -27,10 +27,10 @@ import {
   getFutureModalView,
   getModelView,
   getProbabilityView,
-  getTodayPaceView,
   getTemperatureChartData,
   getWeatherSummary,
 } from "@/lib/dashboard-utils";
+import { getTodayPaceView } from "@/lib/pace-utils";
 import { dashboardClient } from "@/lib/dashboard-client";
 import {
   normalizeObservationSourceCode,