Restructures project with feature-based organization

Refactors project structure to support modular, feature-driven development

Introduces comprehensive language localization support
Adds menu management with role-based access control
Implements dynamic sidebar and theme switching capabilities

Enhances project scalability and maintainability

app/Features/Language/Services/JsonLocalizationService.cs

@@ -0,0 +1,48 @@
+using System.Text.Json;
+using CalendarServer.Features.Language.Models;
+
+namespace CalendarServer.Features.Language.Services;
+
+public class JsonLocalizationService : ILocalizationService
+{
+    private readonly string _translationsPath;
+
+    public JsonLocalizationService(IWebHostEnvironment env)
+    {
+        _translationsPath = Path.Combine(env.ContentRootPath, "Features", "Language", "Translations");
+    }
+
+    public string CurrentCulture => "en";
+
+    public string Get(string key, string? culture = null)
+    {
+        culture ??= CurrentCulture;
+        var filePath = Path.Combine(_translationsPath, $"{culture}.json");
+
+        if (!File.Exists(filePath))
+            return key;
+
+        var json = File.ReadAllText(filePath);
+        var doc = JsonDocument.Parse(json);
+
+        var parts = key.Split('.');
+        JsonElement current = doc.RootElement;
+
+        foreach (var part in parts)
+        {
+            if (!current.TryGetProperty(part, out current))
+                return key;
+        }
+
+        return current.GetString() ?? key;
+    }
+
+    public IEnumerable<SupportedCulture> GetSupportedCultures()
+    {
+        return new List<SupportedCulture>
+        {
+            new() { Code = "da", Name = "Danish", NativeName = "Dansk" },
+            new() { Code = "en", Name = "English", NativeName = "English" }
+        };
+    }
+}