fix(offline): retry pending sync with a cooloff instead of one shot

The auto-flush that runs when reconnecting (or turning Offline Mode
back off) only ever tried once — any operation that still failed on
that attempt sat stuck until the user manually hit Retry or
connectivity changed again. Now retries every 5 minutes for as long as
anything's still pending and the signal stays on, stopping on its own
once the queue is empty. Full Local Sync's existing 20-minute loop is
unaffected/separate.

Outpost/Root/RootView.swift

@@ -50,12 +50,26 @@ struct RootView: View {
         // off — no need to wait for the user to open Settings and hit Retry.
         // Also catches Full Local Sync back up immediately, rather than
         // leaving it to wait out the rest of the periodic loop below.
+        //
+        // The flush itself gets a retry loop with a cooloff, not just one
+        // attempt: a single transient failure (one bad operation, a blip
+        // mid-flush) used to leave everything else stuck until the user
+        // manually hit Retry or connectivity changed again. Keeps retrying
+        // every 5 minutes for as long as *anything* is still pending and
+        // this signal stays on — stops on its own once the queue is empty,
+        // and `.task(id:)` cancels/restarts it automatically if
+        // isEffectivelyOnline flips again in the meantime.
         .task(id: isEffectivelyOnline) {
             guard isEffectivelyOnline, let cachingClient = session.cachingClient else { return }
-            _ = await cachingClient.flushPendingOperations()
             if isFullLocalSyncEnabled {
                 _ = await cachingClient.performFullSync()
             }
+            while !Task.isCancelled {
+                _ = await cachingClient.flushPendingOperations()
+                let remaining = await cachingClient.pendingOperations()
+                guard !remaining.isEmpty else { break }
+                try? await Task.sleep(for: .seconds(300))
+            }
         }
         // Fully automatic — this is the only place Full Local Sync actually
         // runs from (Settings' "Sync Now" is just an on-demand nudge at the