feat(configmanager): integrate SecureStore for credential management

Add SecureStore integration to ConfigManager for secure handling of connection
strings and sensitive configuration values. Includes store/secret management
UI, encrypted .store file support, and comprehensive test coverage.

NEW/src/Utils/JdeScoping.ConfigManager/Constants/SecureStoreFileExtensions.cs

@@ -0,0 +1,21 @@
+namespace JdeScoping.ConfigManager.Constants;
+
+/// <summary>
+/// Centralized constants for secure store file extensions and patterns used in file dialogs.
+/// </summary>
+public static class SecureStoreFileExtensions
+{
+    // SecureStore files
+    public const string StorePattern = "*.json";
+    public const string StoreExtension = ".json";
+    public const string StoreTypeName = "SecureStore Files";
+
+    // Key files
+    public const string KeyPattern = "*.key";
+    public const string KeyExtension = ".key";
+    public const string KeyTypeName = "Key Files";
+
+    // All files
+    public const string AllFilesPattern = "*.*";
+    public const string AllFilesTypeName = "All Files";
+}