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/Models/Entities/SecretMetadata.cs

@@ -0,0 +1,21 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace OTSSignsOrchestrator.Core.Models.Entities;
+
+public class SecretMetadata
+{
+    [Key]
+    public Guid Id { get; set; } = Guid.NewGuid();
+
+    [Required, MaxLength(200)]
+    public string Name { get; set; } = string.Empty;
+
+    public bool IsGlobal { get; set; }
+
+    [MaxLength(100)]
+    public string? CustomerName { get; set; }
+
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+    public DateTime? LastRotatedAt { get; set; }
+}