fix: NAS operation timeouts, fast-path warm-up, 30-min stale threshold

Three changes that together eliminate the "Checking…" stall and excessive NAS
rescanning without requiring a database migration:

NASManifestCache: extend stale threshold from 5 min to 30 min. directoryCount
is now updated incrementally after every upload, and PHPhotoLibraryChangeObserver
keeps LocalPhotoIndex current — a full NAS roundtrip every 5 min was redundant
and forced the expensive reconcile path far more often than necessary.

BackupStatusService: add withTimeout(_:work:) using a racing ThrowingTaskGroup
so NAS operations (SMB connect, manifest download, directory listing) fail fast
instead of hanging indefinitely when the NAS is slow or unreachable. Timeouts:
15s for connect, 12s for manifest download, 12s for directory listings. On
timeout, BackupError.timeout is caught separately to preserve cached counts
instead of marking connectionState = .offline.

BackupStatusService: call LocalPhotoIndex.shared.loadOrBuild() at the start of
performRefresh before checking localIndexCount. Without this, AppDelegate's
concurrent loadOrBuild() task races with the first onActive() trigger; if it
loses, localIndexCount == 0 and the fast path is bypassed, forcing a full NAS
roundtrip on every cold launch.

Co-Authored-By: Kutesir <kutesir@provoc.ug>
Co-Authored-By: Sentry <sentry@provoc.ug>

Services/BackupStatusService.swift

@@ -100,6 +100,11 @@ final class BackupStatusService: NSObject, ObservableObject {
             return
         }
 
+        // Ensure LocalPhotoIndex is loaded from disk before reconcile.
+        // loadOrBuild() is a fast no-op when already in memory; on cold launch it
+        // reads the cached JSON so the fast path (skip NAS roundtrip) can fire.
+        await LocalPhotoIndex.shared.loadOrBuild()
+
         lastFullRefresh = Date()
         isRefreshing = true
         refreshError = nil
@@ -110,6 +115,13 @@ final class BackupStatusService: NSObject, ObservableObject {
             log.info("Refresh completed — phone=\(self.snapshot.phoneTotal) safe=\(self.snapshot.alreadySafe)")
         } catch is CancellationError {
             log.info("Refresh cancelled")
+        } catch BackupError.timeout {
+            // NAS did not respond within the timeout window.
+            // Retain cached counts so the UI shows useful data instead of zeroes.
+            log.warning("Refresh timed out — retaining cached state")
+            refreshError = "NAS not responding — using last known state"
+            snapshot.lastCheckedAt = Date()
+            saveSnapshot()
         } catch {
             log.error("Refresh failed: \(error.localizedDescription)")
             refreshError = error.localizedDescription
@@ -179,12 +191,19 @@ final class BackupStatusService: NSObject, ObservableObject {
         // ── Step 2: NAS connection ────────────────────────────────────────
         let transfer: any NASTransferProtocol = conn.nasProtocol == .smb ? SMBService() : SFTPService()
         do {
-            try await transfer.connect(
-                to: conn.host, port: conn.port,
-                username: conn.username, password: conn.password
-            )
+            try await Self.withTimeout(15) {
+                try await transfer.connect(
+                    to: conn.host, port: conn.port,
+                    username: conn.username, password: conn.password
+                )
+            }
         } catch {
-            let reason = (error as? BackupError).flatMap { $0.errorDescription } ?? error.localizedDescription
+            let reason: String
+            if case BackupError.timeout = error {
+                reason = "NAS not responding — using last known state"
+            } else {
+                reason = (error as? BackupError).flatMap { $0.errorDescription } ?? error.localizedDescription
+            }
             log.warning("NAS connect failed: \(reason, privacy: .public) — retaining cached counts")
             refreshError = reason
 
@@ -262,7 +281,7 @@ final class BackupStatusService: NSObject, ObservableObject {
     ) async -> ManifestIndex {
         log.info("buildManifestIndex: remotePath=\(conn.remotePath, privacy: .public) manifestFile=\(path, privacy: .public)")
         do {
-            let data = try await transfer.downloadData(at: path)
+            let data = try await Self.withTimeout(12) { try await transfer.downloadData(at: path) }
             log.info("buildManifestIndex: manifest downloaded — \(data.count) bytes")
             // Decode and build index off main actor — JSONDecoder is not cheap for large manifests.
             let decoded: (ManifestIndex, BackupManifest)? = await Task.detached(priority: .utility) {
@@ -279,7 +298,7 @@ final class BackupStatusService: NSObject, ObservableObject {
                 // created. Scan the directory to get the real file count for the NAS Archive
                 // display — but do NOT add directory files as orphan manifest entries.
                 if index.totalCount <= 1 {
-                    let items = (try? await transfer.listDirectory(at: conn.remotePath)) ?? []
+                    let items = (try? await Self.withTimeout(12) { try await transfer.listDirectory(at: conn.remotePath) }) ?? []
                     let dirCount = items.filter {
                         !$0.isDirectory && !$0.name.hasPrefix(".") && $0.name != BackupManifest.remoteFilename
                     }.count
@@ -297,7 +316,7 @@ final class BackupStatusService: NSObject, ObservableObject {
         }
 
         // Bootstrap: list NAS directory and build filename-only index in background.
-        let items = (try? await transfer.listDirectory(at: conn.remotePath)) ?? []
+        let items = (try? await Self.withTimeout(12) { try await transfer.listDirectory(at: conn.remotePath) }) ?? []
         log.info("buildManifestIndex: bootstrap from \(items.count) items in \(conn.remotePath, privacy: .public)")
         let bootstrapIndex = await Task.detached(priority: .utility) {
             ManifestIndex(nasListing: items)
@@ -424,6 +443,27 @@ final class BackupStatusService: NSObject, ObservableObject {
         }
     }
 
+    // MARK: — Timeout helper
+
+    /// Runs `work` and throws `BackupError.timeout` if it doesn't finish within `seconds`.
+    /// Uses a racing task group so the timeout fires even when the underlying SMB/SFTP
+    /// stack doesn't propagate Swift cooperative cancellation.
+    private nonisolated static func withTimeout<T: Sendable>(
+        _ seconds: TimeInterval,
+        work: @Sendable @escaping () async throws -> T
+    ) async throws -> T {
+        try await withThrowingTaskGroup(of: T.self) { group in
+            group.addTask(priority: .userInitiated) { try await work() }
+            group.addTask(priority: .utility) {
+                try await Task.sleep(nanoseconds: UInt64(seconds * 1_000_000_000))
+                throw BackupError.timeout
+            }
+            defer { group.cancelAll() }
+            guard let result = try await group.next() else { throw BackupError.timeout }
+            return result
+        }
+    }
+
     // MARK: — Cache
 
     private func loadCachedSnapshot() {

Services/NASManifestCache.swift

@@ -14,7 +14,10 @@ actor NASManifestCache {
 
     private var cached: CachedEntry?
     private let diskURL: URL
-    private static let staleInterval: TimeInterval = 5 * 60
+    // 30-minute window: directoryCount is updated incrementally after every upload,
+    // and PHPhotoLibraryChangeObserver keeps LocalPhotoIndex current. A full NAS
+    // roundtrip every 5 minutes was unnecessary and caused "Checking…" stalls.
+    private static let staleInterval: TimeInterval = 30 * 60
 
     private struct CachedEntry: Codable {
         var manifest: BackupManifest