Enhance API endpoints with response type annotations

- Updated various API endpoints to include response type annotations using .Produces<T>() for better documentation and type safety.
- Enhanced activation, admin, user, config, and other endpoints to specify response types, improving clarity for frontend integration.
- Added new DTOs for structured responses in authentication and Telegram-related endpoints.
- Improved overall API schema generation to reflect these changes, ensuring consistency between backend and frontend types.

backend/src/PnvPanel.Api/Endpoints/ActivationEndpoints.cs

@@ -2,6 +2,7 @@ using PnvPanel.Api.Common;
 using PnvPanel.Application.Activation;
 using PnvPanel.Application.Admin.Activation;
 using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
 using PnvPanel.Domain.Activation;
 using PnvPanel.Infrastructure.Identity;
 
@@ -12,16 +13,16 @@ public static class ActivationEndpoints
     public static IEndpointRouteBuilder MapActivationEndpoints(this IEndpointRouteBuilder app)
     {
         var user = app.MapGroup("/api/activation").WithTags("Activation").RequireAuthorization();
-        user.MapGet("/status", GetStatus);
-        user.MapPost("/request", RequestActivation);
+        user.MapGet("/status", GetStatus).Produces<ActivationStatusDto>();
+        user.MapPost("/request", RequestActivation).Produces<ActivationRequestDto>();
 
         var admin = app.MapGroup("/api/admin/activation-requests")
             .WithTags("Admin.Activation")
             .RequireAuthorization(policy => policy.RequireRole(RoleNames.Admin));
 
-        admin.MapGet("", ListRequests);
-        admin.MapPost("/{id:guid}/approve", Approve);
-        admin.MapPost("/{id:guid}/reject", Reject);
+        admin.MapGet("", ListRequests).Produces<PagedList<ActivationRequestAdminDto>>();
+        admin.MapPost("/{id:guid}/approve", Approve).Produces(StatusCodes.Status204NoContent);
+        admin.MapPost("/{id:guid}/reject", Reject).Produces(StatusCodes.Status204NoContent);
 
         return app;
     }