Completes 'available HealthKit trends' for weekly/monthly reports. Adds
HealthKitManager.dailyReference (3 parallel bucketed HKStatisticsCollectionQuery
for steps/active-calories/resting-HR over ~13 months), AnalyticsService.
refreshHealthReference to cache and merge it into DaySamples, and avgSteps/
avgActiveCalories/avgRestingHR on PeriodSummary (nil when absent — honest).
Surfaced in AnalyticsView's weekly/monthly cards.
Verified standalone (swiftc, 8/8): aggregation correct when present, nil when
absent, workout metrics unaffected, reports stay deterministic. Tests added to
AnalyticsEngineTests. This completes all analytics logic — remaining work is the
first Xcode build (device, user-run) to catch any SwiftUI compile issues.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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