feat(backend/auth): add authorization to Lessons endpoints

- Add RequireAuthorization() to POST, PUT, DELETE endpoints
- Add Microsoft.AspNetCore.Authorization using
- Lessons now require JWT token for create, update, delete

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

GermanApp/Presentation/Endpoints/LessonsEndpoints.cs

@@ -1,6 +1,7 @@
 using GermanApp.Application.DTOs;
 using GermanApp.Application.UseCases.Commands;
 using GermanApp.Domain.Interfaces;
+using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 
 namespace GermanApp.Presentation.Endpoints;
@@ -90,6 +91,7 @@ public static class LessonsEndpoints
             var result = await handler.Handle(command, cancellationToken);
             return Results.Created($"/api/lessons/{result.Id}", result);
         })
+        .RequireAuthorization()
         .WithName("CreateLesson")
         .WithOpenApi(operation => new(operation)
         {
@@ -113,6 +115,7 @@ public static class LessonsEndpoints
 
             return Results.Ok(existingLesson.ToDto());
         })
+        .RequireAuthorization()
         .WithName("UpdateLesson")
         .WithOpenApi(operation => new(operation)
         {
@@ -130,6 +133,7 @@ public static class LessonsEndpoints
             await repository.DeleteAsync(lesson);
             return Results.NoContent();
         })
+        .RequireAuthorization()
         .WithName("DeleteLesson")
         .WithOpenApi(operation => new(operation)
         {