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/InstructionTabDto.cs

@@ -0,0 +1,18 @@
+using PnvPanel.Domain.Instructions;
+
+namespace PnvPanel.Application.Instructions;
+
+/// <summary>Один DTO на пользовательскую страницу и админку — у вкладки нет полей, скрытых от юзера
+/// (нет статуса черновик/опубликовано, см. InstructionTab).</summary>
+public sealed record InstructionTabDto(
+    Guid Id,
+    string Title,
+    string Body,
+    int SortOrder,
+    DateTimeOffset CreatedAt,
+    DateTimeOffset? UpdatedAt
+)
+{
+    public static InstructionTabDto FromDomain(InstructionTab tab) =>
+        new(tab.Id, tab.Title, tab.Body, tab.SortOrder, tab.CreatedAt, tab.UpdatedAt);
+}