feat(core): add IContentMoveOperationService interface for Phase 4

Defines interface for Move, Copy, Sort, and Recycle Bin operations.
MoveToRecycleBin deliberately excluded as it requires facade orchestration.

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Co-Authored-By: Claude <noreply@anthropic.com>

src/Umbraco.Core/Services/IContentMoveOperationService.cs

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+// src/Umbraco.Core/Services/IContentMoveOperationService.cs
+using Umbraco.Cms.Core.Models;
+using Umbraco.Cms.Core.Persistence.Querying;
+
+namespace Umbraco.Cms.Core.Services;
+
+/// <summary>
+/// Service for content move, copy, sort, and recycle bin operations.
+/// </summary>
+/// <remarks>
+/// <para>
+/// <strong>Implementation Note:</strong> Do not implement this interface directly.
+/// Instead, inherit from <see cref="ContentServiceBase"/> which provides required
+/// infrastructure (scoping, repository access, auditing). Direct implementation
+/// without this base class will result in missing functionality.
+/// </para>
+/// <para>
+/// This interface is part of the ContentService refactoring initiative (Phase 4).
+/// It extracts move/copy/sort operations into a focused, testable service.
+/// </para>
+/// <para>
+/// <strong>Note:</strong> <c>MoveToRecycleBin</c> is NOT part of this interface because
+/// it orchestrates multiple services (unpublish + move) and belongs in the facade.
+/// </para>
+/// <para>
+/// <strong>Versioning Policy:</strong> This interface follows additive-only changes.
+/// New methods may be added with default implementations. Existing methods will not
+/// be removed or have signatures changed without a 2 major version deprecation period.
+/// </para>
+/// <para>
+/// <strong>Version History:</strong>
+/// <list type="bullet">
+///   <item><description>v1.0 (Phase 4): Initial interface with Move, Copy, Sort, RecycleBin operations</description></item>
+/// </list>
+/// </para>
+/// </remarks>
+/// <since>1.0</since>
+public interface IContentMoveOperationService : IService
+{
+    // Note: #region blocks kept for consistency with existing Umbraco interface patterns
+
+    #region Move Operations
+
+    /// <summary>
+    /// Moves content to a new parent.
+    /// </summary>
+    /// <param name="content">The content to move.</param>
+    /// <param name="parentId">The target parent id, or -1 for root.</param>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The operation result.</returns>
+    /// <remarks>
+    /// If parentId is the recycle bin (-20), this method delegates to MoveToRecycleBin
+    /// behavior (should be called via ContentService facade instead).
+    /// Fires <see cref="Notifications.ContentMovingNotification"/> (cancellable) before move
+    /// and <see cref="Notifications.ContentMovedNotification"/> after successful move.
+    /// </remarks>
+    OperationResult Move(IContent content, int parentId, int userId = Constants.Security.SuperUserId);
+
+    #endregion
+
+    #region Recycle Bin Operations
+
+    /// <summary>
+    /// Empties the content recycle bin.
+    /// </summary>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The operation result.</returns>
+    /// <remarks>
+    /// Fires <see cref="Notifications.ContentEmptyingRecycleBinNotification"/> (cancellable) before emptying
+    /// and <see cref="Notifications.ContentEmptiedRecycleBinNotification"/> after successful empty.
+    /// Content with active relations may be skipped if DisableDeleteWhenReferenced is configured.
+    /// </remarks>
+    OperationResult EmptyRecycleBin(int userId = Constants.Security.SuperUserId);
+
+    /// <summary>
+    /// Empties the content recycle bin asynchronously.
+    /// </summary>
+    /// <param name="userId">The user key performing the operation.</param>
+    /// <returns>The operation result.</returns>
+    Task<OperationResult> EmptyRecycleBinAsync(Guid userId);
+
+    /// <summary>
+    /// Checks whether there is content in the recycle bin.
+    /// </summary>
+    /// <returns>True if the recycle bin has content; otherwise false.</returns>
+    bool RecycleBinSmells();
+
+    /// <summary>
+    /// Gets paged content from the recycle bin.
+    /// </summary>
+    /// <param name="pageIndex">Zero-based page index.</param>
+    /// <param name="pageSize">Page size.</param>
+    /// <param name="totalRecords">Output: total number of records in recycle bin.</param>
+    /// <param name="filter">Optional filter query.</param>
+    /// <param name="ordering">Optional ordering (defaults to Path).</param>
+    /// <returns>Paged content from the recycle bin.</returns>
+    IEnumerable<IContent> GetPagedContentInRecycleBin(
+        long pageIndex,
+        int pageSize,
+        out long totalRecords,
+        IQuery<IContent>? filter = null,
+        Ordering? ordering = null);
+
+    #endregion
+
+    #region Copy Operations
+
+    /// <summary>
+    /// Copies content to a new parent, including all descendants.
+    /// </summary>
+    /// <param name="content">The content to copy.</param>
+    /// <param name="parentId">The target parent id.</param>
+    /// <param name="relateToOriginal">Whether to create a relation to the original.</param>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The copied content, or null if cancelled.</returns>
+    /// <remarks>
+    /// Fires <see cref="Notifications.ContentCopyingNotification"/> (cancellable) before each copy
+    /// and <see cref="Notifications.ContentCopiedNotification"/> after each successful copy.
+    /// The copy is not published regardless of the original's published state.
+    /// </remarks>
+    IContent? Copy(IContent content, int parentId, bool relateToOriginal, int userId = Constants.Security.SuperUserId);
+
+    /// <summary>
+    /// Copies content to a new parent.
+    /// </summary>
+    /// <param name="content">The content to copy.</param>
+    /// <param name="parentId">The target parent id.</param>
+    /// <param name="relateToOriginal">Whether to create a relation to the original.</param>
+    /// <param name="recursive">Whether to copy descendants recursively.</param>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The copied content, or null if cancelled.</returns>
+    IContent? Copy(IContent content, int parentId, bool relateToOriginal, bool recursive, int userId = Constants.Security.SuperUserId);
+
+    #endregion
+
+    #region Sort Operations
+
+    /// <summary>
+    /// Sorts content items by updating their SortOrder.
+    /// </summary>
+    /// <param name="items">The content items in desired order.</param>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The operation result.</returns>
+    /// <remarks>
+    /// Fires <see cref="Notifications.ContentSortingNotification"/> (cancellable) and
+    /// <see cref="Notifications.ContentSavingNotification"/> (cancellable) before sorting.
+    /// Fires <see cref="Notifications.ContentSavedNotification"/>,
+    /// <see cref="Notifications.ContentSortedNotification"/>, and
+    /// <see cref="Notifications.ContentPublishedNotification"/> (if any were published) after.
+    /// </remarks>
+    OperationResult Sort(IEnumerable<IContent> items, int userId = Constants.Security.SuperUserId);
+
+    /// <summary>
+    /// Sorts content items by id in the specified order.
+    /// </summary>
+    /// <param name="ids">The content ids in desired order.</param>
+    /// <param name="userId">The user performing the operation.</param>
+    /// <returns>The operation result.</returns>
+    OperationResult Sort(IEnumerable<int>? ids, int userId = Constants.Security.SuperUserId);
+
+    #endregion
+}