feat: introduce reusable app lists for rules

- AppList @Model with launch migration from legacy inline selections
  (rules with identical selections share one list; idempotent)
- rules point at one app list; Block/Allow Only belongs to the rule and
  is offered only in the Schedule editor (limit kinds sanitize to Block)
- app-list picker sheet (select / create / edit / delete with in-use
  protection) replaces the per-rule selection sheet
- Hard Mode locks app-list editing while any hard rule is blocking
- SwiftData stability: relationships are only wired between managed
  models, and unit tests share one in-memory container (fresh context +
  data wipe per test) — per-test container creation trapped
  intermittently inside SwiftData

OpenAppLock/Views/Rules/RuleDetailSheet.swift

@@ -123,7 +123,8 @@ struct RuleDetailSheet: View {
     }
 
     private var appCountLabel: String {
-        rule.selectionCount == 1 ? "1 App" : "\(rule.selectionCount) Apps"
+        guard let list = rule.appList else { return "No apps" }
+        return "\(list.name) · \(list.appCountLabel)"
     }
 
     private func row(_ label: String, _ value: String) -> some View {