refactor(securestore): store entire connection strings in SecureStore

Eliminates placeholder substitution (${KEY}) in favor of storing complete
connection strings as single encrypted values. SecureStore now auto-creates
entries for all connection strings defined in appsettings. ConfigManager
editor reads/writes values directly to SecureStore.

NEW/src/Utils/JdeScoping.ConfigManager/ViewModels/MainWindowViewModel.cs

@@ -346,14 +346,18 @@ public class MainWindowViewModel : ViewModelBase
                 _secureStoreManager.OpenStore(storePath, keyFilePath);
             }
 
-            // Ensure all required keys exist
-            if (secureStoreConfig.RequiredKeys?.Count > 0)
+            // Ensure all required entries exist (both RequiredKeys and connection strings)
+            var connectionStringNames = _appSettings?.ConnectionStrings?.Entries
+                .Select(e => e.Name)
+                .Where(n => !string.IsNullOrEmpty(n))
+                ?? Enumerable.Empty<string>();
+
+            var requiredKeys = secureStoreConfig.RequiredKeys ?? new List<string>();
+
+            var addedKeys = _secureStoreManager.EnsureAllRequiredEntries(requiredKeys, connectionStringNames);
+            if (addedKeys.Count > 0)
             {
-                var addedKeys = _secureStoreManager.EnsureRequiredKeys(secureStoreConfig.RequiredKeys);
-                if (addedKeys.Count > 0)
-                {
-                    _logger?.LogInformation("Added {Count} missing required keys", addedKeys.Count);
-                }
+                _logger?.LogInformation("Added {Count} missing required SecureStore entries", addedKeys.Count);
             }
         }
         catch (Exception ex)
@@ -575,6 +579,7 @@ public class MainWindowViewModel : ViewModelBase
             "ExcelExport" => new ExcelExportFormViewModel(_appSettings.ExcelExport, MarkAsChanged),
             "ConnectionStrings" when _dialogService != null => new ConnectionStringsFormViewModel(
                 _appSettings.ConnectionStrings,
+                _secureStoreManager,
                 MarkAsChanged,
                 _dialogService,
                 _connectionTestService),