Add instructions management functionality and update related components

- Introduced new endpoints for managing instruction intros and tabs, allowing admins to create, update, and delete instructional content.
- Enhanced the FactoryResetCommandHandler to include the seeding of instruction data during a factory reset.
- Updated the database schema to include InstructionIntro and InstructionTab entities, with corresponding migrations.
- Improved frontend routing and components to support the new instructions section, including a dedicated page for displaying instructions and tabs.
- Enhanced API documentation to reflect the new instruction management features and their expected request/response formats.
- Added localization support for the new instructions functionality in both Russian and English.

backend/src/PnvPanel.Application/Admin/Instructions/DeleteInstructionTabCommandHandler.cs

@@ -0,0 +1,26 @@
+using Microsoft.EntityFrameworkCore;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Admin.Instructions;
+
+public sealed class DeleteInstructionTabCommandHandler(IAppDbContext dbContext)
+    : ICommandHandler<DeleteInstructionTabCommand, Result>
+{
+    public async Task<Result> Handle(
+        DeleteInstructionTabCommand command,
+        CancellationToken cancellationToken
+    )
+    {
+        var tab = await dbContext.InstructionTabs.FirstOrDefaultAsync(
+            t => t.Id == command.TabId,
+            cancellationToken
+        );
+        if (tab is null)
+            return Result.Failure(InstructionErrors.TabNotFound);
+
+        dbContext.InstructionTabs.Remove(tab);
+        return Result.Success();
+    }
+}