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/GitTemplateService.cs

@@ -0,0 +1,161 @@
+using System.Security.Cryptography;
+using System.Text;
+using LibGit2Sharp;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using OTSSignsOrchestrator.Core.Configuration;
+using OTSSignsOrchestrator.Core.Models.DTOs;
+
+namespace OTSSignsOrchestrator.Core.Services;
+
+/// <summary>
+/// Fetches template.yml and template.env from a Git repository using LibGit2Sharp.
+/// Caches clones on disk, keyed by SHA-256 hash of the repo URL.
+/// </summary>
+public class GitTemplateService
+{
+    private readonly GitOptions _options;
+    private readonly ILogger<GitTemplateService> _logger;
+
+    public GitTemplateService(IOptions<GitOptions> options, ILogger<GitTemplateService> logger)
+    {
+        _options = options.Value;
+        _logger = logger;
+    }
+
+    public async Task<TemplateConfig> FetchAsync(string repoUrl, string? pat = null, bool forceRefresh = false)
+    {
+        var cacheKey = ComputeCacheKey(repoUrl);
+        var cacheDir = Path.Combine(_options.CacheDir, cacheKey);
+
+        _logger.LogInformation("Fetching templates from repo (cacheKey={CacheKey}, force={Force})", cacheKey, forceRefresh);
+
+        await Task.Run(() =>
+        {
+            if (!Directory.Exists(cacheDir) || !Repository.IsValid(cacheDir))
+            {
+                CloneRepo(repoUrl, pat, cacheDir);
+            }
+            else if (forceRefresh || IsCacheStale(cacheDir))
+            {
+                FetchLatest(repoUrl, pat, cacheDir);
+            }
+            else
+            {
+                _logger.LogDebug("Using cached clone at {CacheDir}", cacheDir);
+            }
+        });
+
+        var yamlPath = FindFile(cacheDir, "template.yml");
+        var envPath = FindFile(cacheDir, "template.env");
+
+        if (yamlPath == null)
+            throw new FileNotFoundException("template.yml not found in repository root.");
+        if (envPath == null)
+            throw new FileNotFoundException("template.env not found in repository root.");
+
+        var yaml = await File.ReadAllTextAsync(yamlPath);
+        var envLines = (await File.ReadAllLinesAsync(envPath))
+            .Where(l => !string.IsNullOrWhiteSpace(l) && !l.TrimStart().StartsWith('#'))
+            .ToList();
+
+        return new TemplateConfig
+        {
+            Yaml = yaml,
+            EnvLines = envLines,
+            FetchedAt = DateTime.UtcNow
+        };
+    }
+
+    private void CloneRepo(string repoUrl, string? pat, string cacheDir)
+    {
+        _logger.LogInformation("Shallow cloning repo to {CacheDir}", cacheDir);
+
+        if (Directory.Exists(cacheDir))
+            Directory.Delete(cacheDir, recursive: true);
+
+        Directory.CreateDirectory(cacheDir);
+
+        var cloneOpts = new CloneOptions { IsBare = false, RecurseSubmodules = false };
+
+        if (!string.IsNullOrEmpty(pat))
+        {
+            cloneOpts.FetchOptions.CredentialsProvider = (_, _, _) =>
+                new UsernamePasswordCredentials { Username = pat, Password = string.Empty };
+        }
+
+        try
+        {
+            Repository.Clone(repoUrl, cacheDir, cloneOpts);
+        }
+        catch (LibGit2SharpException ex)
+        {
+            _logger.LogError(ex, "Git clone failed for repo (cacheKey={CacheKey})", ComputeCacheKey(repoUrl));
+            throw new InvalidOperationException($"Failed to clone repository. Check URL and credentials. Error: {ex.Message}", ex);
+        }
+    }
+
+    private void FetchLatest(string repoUrl, string? pat, string cacheDir)
+    {
+        _logger.LogInformation("Fetching latest from origin in {CacheDir}", cacheDir);
+
+        try
+        {
+            using var repo = new Repository(cacheDir);
+
+            var fetchOpts = new FetchOptions();
+            if (!string.IsNullOrEmpty(pat))
+            {
+                fetchOpts.CredentialsProvider = (_, _, _) =>
+                    new UsernamePasswordCredentials { Username = pat, Password = string.Empty };
+            }
+
+            var remote = repo.Network.Remotes["origin"];
+            var refSpecs = remote.FetchRefSpecs.Select(x => x.Specification).ToArray();
+            Commands.Fetch(repo, "origin", refSpecs, fetchOpts, "Auto-fetch for template update");
+
+            var trackingBranch = repo.Head.TrackedBranch;
+            if (trackingBranch != null)
+            {
+                repo.Reset(ResetMode.Hard, trackingBranch.Tip);
+            }
+
+            WriteCacheTimestamp(cacheDir);
+        }
+        catch (LibGit2SharpException ex)
+        {
+            _logger.LogError(ex, "Git fetch failed for repo at {CacheDir}", cacheDir);
+            throw new InvalidOperationException($"Failed to fetch latest templates. Error: {ex.Message}", ex);
+        }
+    }
+
+    private bool IsCacheStale(string cacheDir)
+    {
+        var stampFile = Path.Combine(cacheDir, ".fetch-timestamp");
+        if (!File.Exists(stampFile)) return true;
+
+        if (DateTime.TryParse(File.ReadAllText(stampFile), out var lastFetch))
+        {
+            return (DateTime.UtcNow - lastFetch).TotalMinutes > _options.CacheTtlMinutes;
+        }
+        return true;
+    }
+
+    private static void WriteCacheTimestamp(string cacheDir)
+    {
+        var stampFile = Path.Combine(cacheDir, ".fetch-timestamp");
+        File.WriteAllText(stampFile, DateTime.UtcNow.ToString("O"));
+    }
+
+    private static string? FindFile(string dir, string fileName)
+    {
+        var path = Path.Combine(dir, fileName);
+        return File.Exists(path) ? path : null;
+    }
+
+    private static string ComputeCacheKey(string repoUrl)
+    {
+        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(repoUrl));
+        return Convert.ToHexString(hash)[..16].ToLowerInvariant();
+    }
+}