fixed client-reported crashes in the pdf viewer, image picker and prosemirror images, mapped webdav errors to user messages and hardened keychain, cache and push stores against io failures

lib/push/nid_store.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:localstore/localstore.dart';
 
 /// A rendered notification's bookkeeping, keyed by the Nextcloud notification
@@ -40,8 +41,15 @@ class NidStore {
 
   NidStore({Localstore? db}) : _db = db ?? Localstore.instance;
 
-  Future<void> put(NidEntry entry) =>
-      _db.collection(_collection).doc('${entry.nid}').set(entry.toJson());
+  /// Best effort: a full disk must not keep the notification itself from
+  /// being shown — only a later delete-push would then miss the mapping.
+  Future<void> put(NidEntry entry) async {
+    try {
+      await _db.collection(_collection).doc('${entry.nid}').set(entry.toJson());
+    } on Object catch (e) {
+      debugPrint('NidStore.put(${entry.nid}) failed: $e');
+    }
+  }
 
   Future<NidEntry?> get(int nid) async {
     final data = await _db.collection(_collection).doc('$nid').get();