feat: clone Opal's rules feature with hard block enforcement

Rebuild the app around recurring screen-time blocking rules modeled on
Opal's My Apps tab:

- Onboarding with FamilyControls Screen Time authorization
- Apps home with Blocked Apps tiles and live rule cards
- New Rule sheet: Schedule/Time Limit/Open Limit types + preset gallery
- Rule editors: time windows (incl. overnight), day picker, app selection
  via FamilyActivityPicker (Block/Allow Only), rename, Hold to Commit
- Hard Mode: active hard rules cannot be edited, disabled, deleted, or
  unblocked until their window ends; soft rules pause until next window
- Shield enforcement through per-rule ManagedSettingsStore + RuleEnforcer
- 73 unit tests (Swift Testing) + 16 UI tests (XCUITest) with launch-arg
  harness for in-memory storage, mocked authorization, seeded scenarios
- docs/RULES_FEATURE_SPEC.md: spec derived from the reference recording

Known gap: background window transitions and time/open-limit thresholds
need a DeviceActivityMonitor extension; shields currently sync while the
app is running.

Severed/Views/Components/DayOfWeekPicker.swift

@@ -0,0 +1,61 @@
+//
+//  DayOfWeekPicker.swift
+//  Severed
+//
+
+import SwiftUI
+
+/// "On these days:" — seven circular toggles (S M T W T F S) with a
+/// human-readable summary, as in the reference rule editors.
+struct DayOfWeekPicker: View {
+    @Binding var days: Set<Weekday>
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 14) {
+            HStack {
+                Text("On these days:")
+                    .font(.system(size: 15, weight: .semibold))
+                Spacer()
+                Text(days.summary)
+                    .font(.system(size: 14))
+                    .foregroundStyle(Theme.textSecondary)
+            }
+            HStack(spacing: 8) {
+                ForEach(Weekday.displayOrder, id: \.self) { day in
+                    dayToggle(day)
+                }
+            }
+        }
+        .padding(16)
+        .background(Theme.surface, in: RoundedRectangle(cornerRadius: 18))
+    }
+
+    private func dayToggle(_ day: Weekday) -> some View {
+        let isOn = days.contains(day)
+        return Button {
+            if isOn {
+                days.remove(day)
+            } else {
+                days.insert(day)
+            }
+        } label: {
+            Text(day.shortLabel)
+                .font(.system(size: 15, weight: .semibold))
+                .foregroundStyle(isOn ? .black : Theme.textSecondary)
+                .frame(maxWidth: .infinity)
+                .aspectRatio(1, contentMode: .fit)
+                .background(isOn ? Color.white : Theme.surfaceElevated, in: Circle())
+        }
+        .buttonStyle(.plain)
+        .accessibilityIdentifier("dayToggle-\(day.rawValue)")
+        .accessibilityLabel(day.abbreviation)
+        .accessibilityAddTraits(isOn ? .isSelected : [])
+    }
+}
+
+#Preview {
+    @Previewable @State var days = Weekday.weekdays
+    DayOfWeekPicker(days: $days)
+        .padding()
+        .background(Theme.background)
+}