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/DTOs/CreateInstanceDto.cs

@@ -0,0 +1,41 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace OTSSignsOrchestrator.Core.Models.DTOs;
+
+public class CreateInstanceDto
+{
+    [Required, MaxLength(100)]
+    public string CustomerName { get; set; } = string.Empty;
+
+    /// <summary>Exactly 3 lowercase letters used to derive all resource names.</summary>
+    [Required, MaxLength(3), MinLength(3), RegularExpression("^[a-z]{3}$", ErrorMessage = "Abbreviation must be exactly 3 lowercase letters.")]
+    public string CustomerAbbrev { get; set; } = string.Empty;
+
+    /// <summary>SSH host to deploy to.</summary>
+    public Guid? SshHostId { get; set; }
+
+    /// <summary>Pangolin Newt ID (optional — tunnel service excluded if not provided).</summary>
+    [MaxLength(500)]
+    public string? NewtId { get; set; }
+
+    /// <summary>Pangolin Newt Secret (optional — tunnel service excluded if not provided).</summary>
+    [MaxLength(500)]
+    public string? NewtSecret { get; set; }
+
+    // ── CIFS / SMB credentials (optional — falls back to global settings) ──
+
+    [MaxLength(200)]
+    public string? CifsServer { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsShareBasePath { get; set; }
+
+    [MaxLength(200)]
+    public string? CifsUsername { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsPassword { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsExtraOptions { get; set; }
+}

OTSSignsOrchestrator.Core/Models/DTOs/DeploymentResultDto.cs

@@ -0,0 +1,13 @@
+namespace OTSSignsOrchestrator.Core.Models.DTOs;
+
+public class DeploymentResultDto
+{
+    public bool Success { get; set; }
+    public string StackName { get; set; } = string.Empty;
+    public string Message { get; set; } = string.Empty;
+    public string? Output { get; set; }
+    public string? ErrorMessage { get; set; }
+    public int ExitCode { get; set; }
+    public long DurationMs { get; set; }
+    public int ServiceCount { get; set; }
+}

OTSSignsOrchestrator.Core/Models/DTOs/TemplateConfig.cs

@@ -0,0 +1,8 @@
+namespace OTSSignsOrchestrator.Core.Models.DTOs;
+
+public class TemplateConfig
+{
+    public string Yaml { get; set; } = string.Empty;
+    public List<string> EnvLines { get; set; } = new();
+    public DateTime FetchedAt { get; set; } = DateTime.UtcNow;
+}

OTSSignsOrchestrator.Core/Models/DTOs/UpdateInstanceDto.cs

@@ -0,0 +1,43 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace OTSSignsOrchestrator.Core.Models.DTOs;
+
+public class UpdateInstanceDto
+{
+    [MaxLength(500)]
+    public string? TemplateRepoUrl { get; set; }
+
+    [MaxLength(500)]
+    public string? TemplateRepoPat { get; set; }
+
+    [MaxLength(200)]
+    public string? SmtpServer { get; set; }
+
+    [MaxLength(200)]
+    public string? SmtpUsername { get; set; }
+
+    public List<string>? Constraints { get; set; }
+
+    [MaxLength(200)]
+    public string? XiboUsername { get; set; }
+
+    [MaxLength(200)]
+    public string? XiboPassword { get; set; }
+
+    // ── CIFS / SMB credentials (per-instance) ──
+
+    [MaxLength(200)]
+    public string? CifsServer { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsShareBasePath { get; set; }
+
+    [MaxLength(200)]
+    public string? CifsUsername { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsPassword { get; set; }
+
+    [MaxLength(500)]
+    public string? CifsExtraOptions { get; set; }
+}