Align cache eviction to the backend aging model

Retention now mirrors the backend: cached stories age out at RECENT_HOURS (72h,
the active feed window), seen/read markers at 96h (window + buffer), and cached
article bodies at 14 days (raw-article retention). Saved bookmarks stay protected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Jarvis/Store/CacheMaintenance.swift

@@ -7,21 +7,23 @@ import SwiftData
 
 @MainActor
 enum CacheMaintenance {
+    private static let hour: TimeInterval = 3_600
     private static let day: TimeInterval = 86_400
 
-    // Retention windows.
-    private static let seenDays = 30.0      // "seen" markers: only useful while a story is live
-    private static let readDays = 90.0      // read history: small, keep longer
-    private static let articleDays = 30.0   // offline article bodies
-    private static let storyDays = 14.0     // offline story list
+    // Aligned to the backend's aging model:
+    //   RECENT_HOURS = 72  → active feed window; drop cached stories past it
+    //   raw-article retention ~14 days → match for cached article bodies
+    private static let recentHours = 72.0    // backend active window (story list)
+    private static let markerHours = 96.0    // seen/read markers: active window + buffer
+    private static let articleDays = 14.0    // cached article bodies (backend article retention)
 
     /// Age-based eviction. Run on launch. Cheap; protects saved stories.
     static func prune(_ context: ModelContext) {
         let now = Date()
-        let seenCutoff = now.addingTimeInterval(-seenDays * day)
-        let readCutoff = now.addingTimeInterval(-readDays * day)
+        let seenCutoff = now.addingTimeInterval(-markerHours * hour)
+        let readCutoff = now.addingTimeInterval(-markerHours * hour)
         let articleCutoff = now.addingTimeInterval(-articleDays * day)
-        let storyCutoff = now.addingTimeInterval(-storyDays * day)
+        let storyCutoff = now.addingTimeInterval(-recentHours * hour)
 
         // Markers: simple age batch deletes.
         try? context.delete(model: SeenStory.self, where: #Predicate { $0.seenAt < seenCutoff })