sync: a failed persist must not take the sign-in down with it

remember() runs in viewModelScope, where an escaping DataStore IO
exception is a crash. A flow we could not write down costs the reclaim,
not the sign-in the user is in the middle of.

app/src/main/java/de/jeanlucmakiola/agendula/data/sync/PendingLoginFlowStore.kt

@@ -114,8 +114,9 @@ class PendingLoginFlowStore @Inject constructor(
 
             is NextcloudLoginFlow.PollResult.Expired -> forget()
 
-            // Still inside the window, or the server had a moment. Either way the
-            // token is still worth something; the deadline retires it.
+            // Still inside the window, or the server had a moment. Either way
+            // the token is still worth something, so it is left for the next
+            // open; a poll past the deadline answers Expired and clears it.
             NextcloudLoginFlow.PollResult.Pending,
             is NextcloudLoginFlow.PollResult.Failed,
             -> Unit

app/src/main/java/de/jeanlucmakiola/agendula/ui/accounts/AddAccountViewModel.kt

@@ -269,7 +269,12 @@ class AddAccountViewModel @Inject constructor(
         // what the flow's own doc asks for: the browser is a separate task, so
         // dying while the user approves is ordinary, and the poll token is the
         // only way back to the password the server is about to mint.
-        pendingFlow.remember(flow)
+        //
+        // ⚠️ Guarded: a DataStore write can throw, and this runs in
+        // viewModelScope, where an escaping exception takes the app down. A
+        // flow we failed to write down is a reclaim we will not get, not a
+        // reason to lose the sign-in in front of the user.
+        runCatching { pendingFlow.remember(flow) }
         _state.update {
             it.copy(
                 step = AddAccountStep.WaitingForBrowser(hostMismatch = flow.hostMismatch),