fix(mongodb): handle unauthorized listDatabases on admin by falling back to connection database

lib/core/database/mongodb_connection.dart

@@ -45,6 +45,24 @@ class MongoConnection {
   Db? _db;
   bool _isConnected = false;
 
+  /// Effective database name from [database] configuration or connection URI path.
+  String? get effectiveDatabase {
+    if (database != null && database!.trim().isNotEmpty) {
+      return database!.trim();
+    }
+    final rawUri = _sessionUri ?? _connectionString;
+    if (rawUri != null && rawUri.isNotEmpty) {
+      try {
+        final parsed = Uri.parse(rawUri);
+        final path = parsed.path.replaceFirst('/', '').trim();
+        if (path.isNotEmpty) {
+          return path;
+        }
+      } catch (_) {}
+    }
+    return null;
+  }
+
   /// Scrubs sensitive in-memory credentials once the network handshake completes.
   ///
   /// Getters [password] and [connectionString] become null. The live session
@@ -298,6 +316,12 @@ class MongoConnection {
           .where((name) => name.isNotEmpty)
           .toList();
     } catch (e) {
+      final fallback = effectiveDatabase;
+      if (fallback != null &&
+          fallback.isNotEmpty &&
+          fallback.toLowerCase() != 'admin') {
+        return [fallback];
+      }
       rethrow;
     }
   }

lib/features/mongodb/mongo_databases_view.dart

@@ -135,6 +135,19 @@ class _MongoDatabasesViewState extends State<MongoDatabasesView> {
         });
       }
     } catch (e) {
+      final fallback = _connection?.effectiveDatabase;
+      if (fallback != null &&
+          fallback.isNotEmpty &&
+          fallback.toLowerCase() != 'admin') {
+        if (mounted) {
+          setState(() {
+            _databases = [_DatabaseInfo(name: fallback, sizeOnDisk: null)];
+            _isLoading = false;
+            _error = null;
+          });
+        }
+        return;
+      }
       if (mounted) {
         setState(() {
           _error = 'Failed to list databases: $e';

test/core/database/mongodb_connection_fallback_test.dart

@@ -0,0 +1,35 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/database/mongodb_connection.dart';
+
+void main() {
+  group('MongoConnection.effectiveDatabase', () {
+    test('returns database from property if configured', () {
+      final conn = MongoConnection(
+        id: 1,
+        name: 'test',
+        host: 'localhost',
+        database: '  analytics_prod  ',
+      );
+      expect(conn.effectiveDatabase, 'analytics_prod');
+    });
+
+    test('returns database from connectionString URI path if database property is omitted', () {
+      final conn = MongoConnection(
+        id: 1,
+        name: 'test',
+        host: 'localhost',
+        connectionString: 'mongodb://user:secret@mongo.cloud.com:27017/tenant_db?ssl=true',
+      );
+      expect(conn.effectiveDatabase, 'tenant_db');
+    });
+
+    test('returns null when neither property nor URI has a database', () {
+      final conn = MongoConnection(
+        id: 1,
+        name: 'test',
+        host: 'localhost',
+      );
+      expect(conn.effectiveDatabase, isNull);
+    });
+  });
+}