analytics(healthkit): wire historical HealthKit reference into reports (KC-51 ph4e)

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>

KisaniCal/ContentView.swift

@@ -114,6 +114,8 @@ struct ContentView: View {
             Task {
                 await workoutVM.syncFromHealthKit()
                 NotificationManager.shared.reschedule(workoutVM: workoutVM, taskVM: taskVM)
+                await AnalyticsService.shared.refreshHealthReference()
+                AnalyticsService.shared.reconcile(using: workoutVM)
             }
         }
         .onChange(of: scenePhase) { phase in