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/Instructions/ListInstructionTabsQueryHandler.cs

@@ -0,0 +1,31 @@
+using Microsoft.EntityFrameworkCore;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Instructions;
+
+public sealed class ListInstructionTabsQueryHandler(IAppDbContext dbContext)
+    : IQueryHandler<ListInstructionTabsQuery, Result<IReadOnlyList<InstructionTabDto>>>
+{
+    public async Task<Result<IReadOnlyList<InstructionTabDto>>> Handle(
+        ListInstructionTabsQuery query,
+        CancellationToken cancellationToken
+    )
+    {
+        var tabs = await dbContext
+            .InstructionTabs.AsNoTracking()
+            .OrderBy(t => t.SortOrder)
+            .Select(t => new InstructionTabDto(
+                t.Id,
+                t.Title,
+                t.Body,
+                t.SortOrder,
+                t.CreatedAt,
+                t.UpdatedAt
+            ))
+            .ToListAsync(cancellationToken);
+
+        return Result.Success<IReadOnlyList<InstructionTabDto>>(tabs);
+    }
+}