Add user-specific persistent grid/band layouts support

Implemented user-customizable, persistent grid and band layouts for CatalogsGrid and MassDataGrid. Added backend API, database entity, and repository for storing layouts per user. Refactored grids to support dynamic band/column rendering, layout management UI, and per-user storage via localStorage and the new API. Registered all necessary services and updated data context. Enables flexible, user-specific grid experiences with saved layouts.

DbFirst.API/Controllers/LayoutsController.cs

@@ -0,0 +1,94 @@
+using System.Text;
+using DbFirst.Application.Repositories;
+using DbFirst.Domain.Entities;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DbFirst.API.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+public class LayoutsController : ControllerBase
+{
+    private readonly ILayoutRepository _repository;
+
+    public LayoutsController(ILayoutRepository repository)
+    {
+        _repository = repository;
+    }
+
+    [HttpGet]
+    public async Task<ActionResult<LayoutDto>> Get([FromQuery] string layoutType, [FromQuery] string layoutKey, [FromQuery] string userName, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(layoutType) || string.IsNullOrWhiteSpace(layoutKey) || string.IsNullOrWhiteSpace(userName))
+        {
+            return BadRequest("layoutType, layoutKey und userName sind erforderlich.");
+        }
+
+        var entity = await _repository.GetAsync(layoutType, layoutKey, userName, cancellationToken);
+        if (entity == null)
+        {
+            return NotFound();
+        }
+
+        return Ok(Map(entity));
+    }
+
+    [HttpPost]
+    public async Task<ActionResult<LayoutDto>> Upsert(LayoutDto dto, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(dto.LayoutType) || string.IsNullOrWhiteSpace(dto.LayoutKey) || string.IsNullOrWhiteSpace(dto.UserName))
+        {
+            return BadRequest("LayoutType, LayoutKey und UserName sind erforderlich.");
+        }
+
+        var data = string.IsNullOrWhiteSpace(dto.LayoutData)
+            ? Array.Empty<byte>()
+            : Encoding.UTF8.GetBytes(dto.LayoutData);
+
+        try
+        {
+            var entity = await _repository.UpsertAsync(dto.LayoutType, dto.LayoutKey, dto.UserName, data, cancellationToken);
+            return Ok(Map(entity));
+        }
+        catch (Exception ex)
+        {
+            var detail = ex.InnerException?.Message ?? ex.Message;
+            return Problem(detail: detail, statusCode: StatusCodes.Status500InternalServerError);
+        }
+    }
+
+    [HttpDelete]
+    public async Task<IActionResult> Delete([FromQuery] string layoutType, [FromQuery] string layoutKey, [FromQuery] string userName, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(layoutType) || string.IsNullOrWhiteSpace(layoutKey) || string.IsNullOrWhiteSpace(userName))
+        {
+            return BadRequest("layoutType, layoutKey und userName sind erforderlich.");
+        }
+
+        var deleted = await _repository.DeleteAsync(layoutType, layoutKey, userName, cancellationToken);
+        return deleted ? NoContent() : NotFound();
+    }
+
+    private static LayoutDto Map(SmfLayout entity)
+    {
+        var layoutData = entity.LayoutData.Length == 0
+            ? string.Empty
+            : Encoding.UTF8.GetString(entity.LayoutData);
+
+        return new LayoutDto
+        {
+            LayoutType = entity.LayoutType,
+            LayoutKey = entity.LayoutKey,
+            UserName = entity.UserName,
+            LayoutData = layoutData
+        };
+    }
+
+    public sealed class LayoutDto
+    {
+        public string LayoutType { get; set; } = string.Empty;
+        public string LayoutKey { get; set; } = string.Empty;
+        public string UserName { get; set; } = string.Empty;
+        public string LayoutData { get; set; } = string.Empty;
+    }
+}