feat: Add main application views and structure

- Implemented CreateInstanceView for creating new instances.
- Added HostsView for managing SSH hosts with CRUD operations.
- Created InstancesView for displaying and managing instances.
- Developed LogsView for viewing operation logs.
- Introduced SecretsView for managing secrets associated with hosts.
- Established SettingsView for configuring application settings.
- Created MainWindow as the main application window with navigation.
- Added app manifest and configuration files for logging and settings.

OTSSignsOrchestrator.Core/Services/IDockerSecretsService.cs

@@ -0,0 +1,19 @@
+namespace OTSSignsOrchestrator.Core.Services;
+
+/// <summary>
+/// Abstraction for Docker Swarm secret operations.
+/// Implementations may use Docker.DotNet, local CLI, or SSH-based remote execution.
+/// </summary>
+public interface IDockerSecretsService
+{
+    Task<(bool Created, string SecretId)> EnsureSecretAsync(string name, string value, bool rotate = false);
+    Task<List<SecretListItem>> ListSecretsAsync();
+    Task<bool> DeleteSecretAsync(string name);
+}
+
+public class SecretListItem
+{
+    public string Id { get; set; } = string.Empty;
+    public string Name { get; set; } = string.Empty;
+    public DateTime CreatedAt { get; set; }
+}