Add restore functionality for template management and enhance related components

Implemented a new endpoint for restoring templates to their last applied state, allowing users to revert changes made since the last application. Updated the ScheduleTemplate class to include a snapshot of the last applied state, enabling rollback capabilities. Enhanced the frontend with a restore button in the ChannelDetail component, providing users with a confirmation prompt before executing the restore action. Localization updates were made to support new UI strings in both English and Russian, improving the overall user experience in template management.

backend/src/TeleWave.Infrastructure/Migrations/20260727053636_TemplateAppliedSnapshot.cs

@@ -0,0 +1,27 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace TeleWave.Infrastructure.Migrations
+{
+    /// <inheritdoc />
+    public partial class TemplateAppliedSnapshot : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "AppliedSnapshotJson",
+                table: "ScheduleTemplates",
+                type: "jsonb",
+                nullable: true
+            );
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(name: "AppliedSnapshotJson", table: "ScheduleTemplates");
+        }
+    }
+}

backend/src/TeleWave.Infrastructure/Migrations/AppDbContextModelSnapshot.cs

@@ -944,6 +944,9 @@ namespace TeleWave.Infrastructure.Migrations
                     b.Property<int>("AppliedRevision")
                         .HasColumnType("integer");
 
+                    b.Property<string>("AppliedSnapshotJson")
+                        .HasColumnType("jsonb");
+
                     b.Property<Guid>("ChannelId")
                         .HasColumnType("uuid");
 

backend/src/TeleWave.Infrastructure/Persistence/Configurations/ScheduleTemplateConfiguration.cs

@@ -11,6 +11,7 @@ public class ScheduleTemplateConfiguration : IEntityTypeConfiguration<ScheduleTe
     {
         builder.Property(x => x.Name).IsRequired().HasMaxLength(256);
         builder.Property(x => x.RulesJson).HasColumnType("jsonb");
+        builder.Property(x => x.AppliedSnapshotJson).HasColumnType("jsonb");
         builder.HasIndex(x => x.ChannelId);
 
         builder