Enhance documentation with new features: added dark/light/system theme support, instructions page, and application catalog. Updated API and domain model for app management and automatic migrations on startup. Improved frontend structure with new routes and features for user instructions and app management.

backend/src/PnvPanel.Application/Common/Models/Result.cs

@@ -0,0 +1,37 @@
+namespace PnvPanel.Application.Common.Models;
+
+public class Result
+{
+    public bool IsSuccess { get; }
+    public Error Error { get; }
+
+    protected Result(bool isSuccess, Error error)
+    {
+        if (isSuccess && error != Error.None)
+            throw new InvalidOperationException("Успешный результат не может содержать ошибку.");
+        if (!isSuccess && error == Error.None)
+            throw new InvalidOperationException("Неуспешный результат обязан содержать ошибку.");
+
+        IsSuccess = isSuccess;
+        Error = error;
+    }
+
+    public static Result Success() => new(true, Error.None);
+    public static Result Failure(Error error) => new(false, error);
+
+    public static Result<T> Success<T>(T value) => new(value, true, Error.None);
+    public static Result<T> Failure<T>(Error error) => new(default, false, error);
+}
+
+public class Result<T> : Result
+{
+    private readonly T? _value;
+
+    internal Result(T? value, bool isSuccess, Error error) : base(isSuccess, error) => _value = value;
+
+    public T Value => IsSuccess
+        ? _value!
+        : throw new InvalidOperationException("Нельзя получить значение неуспешного результата.");
+
+    public static implicit operator Result<T>(T value) => Success(value);
+}