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

test/api/errors/error_mapper_test.dart

@@ -14,6 +14,9 @@ import 'package:marianum_mobile/api/errors/parse_exception.dart';
 import 'package:marianum_mobile/api/errors/permission_exception.dart';
 import 'package:nextcloud/nextcloud.dart';
 
+(String, bool) errorUserMessageAndRetry(Object error) =>
+    (errorToUserMessage(error), errorAllowsRetry(error));
+
 void main() {
   group('errorToUserMessage', () {
     test('null falls back to the default message', () {
@@ -165,6 +168,96 @@ void main() {
       expect(errorToUserMessage(ex), contains('Zu viele Anfragen'));
       expect(errorAllowsRetry(ex), isTrue);
     });
+
+    String davBody(String exception, String message) =>
+        '<?xml version="1.0" encoding="utf-8"?>\n'
+        '<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">\n'
+        '  <s:exception>Sabre\\DAV\\Exception\\$exception</s:exception>\n'
+        '  <s:message>$message</s:message>\n'
+        '</d:error>';
+
+    test('parseDavError extracts class and message', () {
+      final dav = parseDavError(
+        davBody(
+          'MethodNotAllowed',
+          'The resource you tried to create already exists',
+        ),
+      );
+      expect(dav?.exception, 'MethodNotAllowed');
+      expect(dav?.message, 'The resource you tried to create already exists');
+      expect(parseDavError('<html>nope</html>'), isNull);
+    });
+
+    test('MKCOL 405 on an existing folder says so and allows no retry', () {
+      final ex = DynamiteApiException(
+        405,
+        const {},
+        davBody(
+          'MethodNotAllowed',
+          'The resource you tried to create already exists',
+        ),
+      );
+      expect(errorToUserMessage(ex), contains('existiert bereits'));
+      expect(
+        errorToTechnicalDetails(ex),
+        'HTTP 405 MethodNotAllowed: The resource you tried to create already exists',
+      );
+      expect(errorAllowsRetry(ex), isFalse);
+    });
+
+    test('other DAV exceptions map to their own messages', () {
+      expect(
+        errorToUserMessage(
+          DynamiteApiException(
+            412,
+            const {},
+            davBody('PreconditionFailed', 'x'),
+          ),
+        ),
+        contains('Zielort'),
+      );
+      expect(
+        errorToUserMessage(
+          DynamiteApiException(409, const {}, davBody('Conflict', 'x')),
+        ),
+        contains('übergeordnete Ordner'),
+      );
+      expect(
+        errorUserMessageAndRetry(
+          DynamiteApiException(423, const {}, davBody('Locked', 'x')),
+        ),
+        (
+          'Der Eintrag wird gerade bearbeitet. Bitte versuche es gleich erneut.',
+          true,
+        ),
+      );
+      expect(
+        errorToUserMessage(
+          DynamiteApiException(
+            507,
+            const {},
+            davBody('InsufficientStorage', 'x'),
+          ),
+        ),
+        contains('Speicherplatz'),
+      );
+    });
+
+    test(
+      'unknown DAV exceptions keep the status mapping but name the class',
+      () {
+        final ex = DynamiteApiException(
+          404,
+          const {},
+          davBody('NotFound', 'File not found'),
+        );
+        expect(errorToUserMessage(ex), const NotFoundException().userMessage);
+        expect(
+          errorToTechnicalDetails(ex),
+          'HTTP 404 NotFound: File not found',
+        );
+      },
+    );
   });
 
   group('errorToTechnicalDetails', () {