Fix blog category selection and empty state rendering

src/TaxBaik.Application/DTOs/CreateBlogPostDto.cs

@@ -4,7 +4,7 @@ public class CreateBlogPostDto
 {
     public required string Title { get; set; }
     public required string Content { get; set; }
-    public int? CategoryId { get; set; }
+    public int CategoryId { get; set; }
     public string? Tags { get; set; }
     public string? SeoTitle { get; set; }
     public string? SeoDescription { get; set; }
@@ -18,7 +18,7 @@ public class BlogPostResponseDto
     public int Id { get; set; }
     public string Title { get; set; } = string.Empty;
     public string Content { get; set; } = string.Empty;
-    public int? CategoryId { get; set; }
+    public int CategoryId { get; set; }
     public string? Tags { get; set; }
     public string? SeoTitle { get; set; }
     public string? SeoDescription { get; set; }

src/TaxBaik.Application/DTOs/Validators.cs

@@ -8,6 +8,7 @@ public sealed class CreateBlogPostDtoValidator : AbstractValidator<CreateBlogPos
     {
         RuleFor(x => x.Title).NotEmpty().MaximumLength(ValidationRules.TitleMaxLength);
         RuleFor(x => x.Content).NotEmpty().MinimumLength(ValidationRules.MessageMinLength).MaximumLength(ValidationRules.ContentMaxLength);
+        RuleFor(x => x.CategoryId).GreaterThan(0);
         RuleFor(x => x.Tags).MaximumLength(ValidationRules.TagsMaxLength);
         RuleFor(x => x.SeoTitle).MaximumLength(ValidationRules.SeoTitleMaxLength);
         RuleFor(x => x.SeoDescription).MaximumLength(ValidationRules.SeoDescriptionMaxLength);

src/TaxBaik.Web/Pages/Admin/Blog/Create.cshtml

@@ -2,6 +2,7 @@
 @model TaxBaik.Web.Pages.Admin.Blog.CreateModel
 @{
     ViewData["Title"] = "블로그 등록";
+    ViewData["BlogCategories"] = Model.Categories;
 }
 
 @await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(

src/TaxBaik.Web/Pages/Admin/Blog/Create.cshtml.cs

@@ -3,12 +3,13 @@ using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
 using TaxBaik.Application.DTOs;
 using TaxBaik.Application.Services;
+using TaxBaik.Domain.Entities;
 using TaxBaik.Web.Services;
 
 namespace TaxBaik.Web.Pages.Admin.Blog;
 
 [Authorize(AuthenticationSchemes = AdminAuthDefaults.Scheme)]
-public class CreateModel(BlogService blogService) : PageModel
+public class CreateModel(BlogService blogService, CategoryService categoryService) : PageModel
 {
     [BindProperty]
     public CreateBlogPostDto Input { get; set; } = new()
@@ -17,14 +18,47 @@ public class CreateModel(BlogService blogService) : PageModel
         Title = string.Empty
     };
 
-    public IActionResult OnGet() => Page();
+    public IReadOnlyList<Category> Categories { get; private set; } = [];
+
+    public async Task<IActionResult> OnGetAsync(CancellationToken ct)
+    {
+        Categories = (await EnsureCategoriesAsync(ct)).ToList();
+        if (Categories.Count > 0)
+            Input.CategoryId = Categories[0].Id;
+
+        return Page();
+    }
 
     public async Task<IActionResult> OnPostAsync(CancellationToken ct)
     {
+        Categories = (await EnsureCategoriesAsync(ct)).ToList();
         if (!ModelState.IsValid)
             return Page();
 
         await blogService.CreateAsync(Input, ct);
         return RedirectToPage("/Admin/Blog/Index");
     }
+
+    private async Task<IEnumerable<Category>> EnsureCategoriesAsync(CancellationToken ct)
+    {
+        var categories = (await categoryService.GetAllAsync(ct)).ToList();
+        if (categories.Count > 0)
+            return categories;
+
+        var defaults = new[]
+        {
+            ("사업자 세무", "business-tax", 1),
+            ("부동산 세금", "real-estate-tax", 2),
+            ("종합소득세", "income-tax", 3),
+            ("부가가치세", "vat", 4),
+            ("가족자산·증여", "family-asset", 5)
+        };
+
+        foreach (var (name, slug, sortOrder) in defaults)
+        {
+            await categoryService.CreateAsync(name, null, ct);
+        }
+
+        return await categoryService.GetAllAsync(ct);
+    }
 }

src/TaxBaik.Web/Pages/Admin/Blog/Edit.cshtml

@@ -3,6 +3,7 @@
 @{
     ViewData["Title"] = "블로그 수정";
     ViewData["BlogEditorId"] = Model.Id;
+    ViewData["BlogCategories"] = Model.Categories;
 }
 
 @await Html.PartialAsync("_BlogEditor", new TaxBaik.Web.Pages.Shared.BlogEditorModel(

src/TaxBaik.Web/Pages/Admin/Blog/Edit.cshtml.cs

@@ -3,12 +3,13 @@ using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
 using TaxBaik.Application.DTOs;
 using TaxBaik.Application.Services;
+using TaxBaik.Domain.Entities;
 using TaxBaik.Web.Services;
 
 namespace TaxBaik.Web.Pages.Admin.Blog;
 
 [Authorize(AuthenticationSchemes = AdminAuthDefaults.Scheme)]
-public class EditModel(BlogService blogService) : PageModel
+public class EditModel(BlogService blogService, CategoryService categoryService) : PageModel
 {
     [BindProperty(SupportsGet = true)]
     public int Id { get; set; }
@@ -20,17 +21,20 @@ public class EditModel(BlogService blogService) : PageModel
         Title = string.Empty
     };
 
+    public IReadOnlyList<Category> Categories { get; private set; } = [];
+
     public async Task<IActionResult> OnGetAsync(CancellationToken ct)
     {
         var post = await blogService.GetByIdAsync(Id, ct);
         if (post is null)
             return NotFound();
 
+        Categories = (await EnsureCategoriesAsync(ct)).ToList();
         Input = new CreateBlogPostDto
         {
             Title = post.Title,
             Content = post.Content,
-            CategoryId = post.CategoryId,
+            CategoryId = post.CategoryId ?? 0,
             Tags = post.Tags,
             SeoTitle = post.SeoTitle,
             SeoDescription = post.SeoDescription,
@@ -44,6 +48,7 @@ public class EditModel(BlogService blogService) : PageModel
 
     public async Task<IActionResult> OnPostAsync(CancellationToken ct)
     {
+        Categories = (await EnsureCategoriesAsync(ct)).ToList();
         if (!ModelState.IsValid)
             return Page();
 
@@ -59,4 +64,27 @@ public class EditModel(BlogService blogService) : PageModel
         await blogService.DeleteAsync(Id, ct);
         return RedirectToPage("/Admin/Blog/Index");
     }
+
+    private async Task<IEnumerable<Category>> EnsureCategoriesAsync(CancellationToken ct)
+    {
+        var categories = (await categoryService.GetAllAsync(ct)).ToList();
+        if (categories.Count > 0)
+            return categories;
+
+        var defaults = new[]
+        {
+            ("사업자 세무", "business-tax", 1),
+            ("부동산 세금", "real-estate-tax", 2),
+            ("종합소득세", "income-tax", 3),
+            ("부가가치세", "vat", 4),
+            ("가족자산·증여", "family-asset", 5)
+        };
+
+        foreach (var (name, slug, sortOrder) in defaults)
+        {
+            await categoryService.CreateAsync(name, null, ct);
+        }
+
+        return await categoryService.GetAllAsync(ct);
+    }
 }

src/TaxBaik.Web/Pages/Shared/BlogEditorModel.cs

@@ -3,7 +3,7 @@ namespace TaxBaik.Web.Pages.Shared;
 public sealed record BlogEditorModel(
     string Title,
     string Content,
-    int? CategoryId,
+    int CategoryId,
     bool IsPublished,
     string? ThumbnailUrl,
     string? SeoTitle,

src/TaxBaik.Web/Pages/Shared/_BlogEditor.cshtml

@@ -43,7 +43,20 @@
                     <div class="row g-3 blog-meta-grid">
                         <div class="col-md-4">
                             <label class="form-label" for="Input_CategoryId">카테고리</label>
-                            <input class="form-control" id="Input_CategoryId" name="Input.CategoryId" value="@Model.CategoryId" />
+                            <select class="form-select" id="Input_CategoryId" name="Input.CategoryId" required>
+                                @foreach (var category in (ViewData["BlogCategories"] as IEnumerable<TaxBaik.Domain.Entities.Category>) ?? [])
+                                {
+                                    if (category.Id == Model.CategoryId)
+                                    {
+                                        <option value="@category.Id" selected>@category.Name</option>
+                                    }
+                                    else
+                                    {
+                                        <option value="@category.Id">@category.Name</option>
+                                    }
+                                }
+                            </select>
+                            <span class="text-danger small" data-valmsg-for="Input.CategoryId" data-valmsg-replace="true"></span>
                         </div>
                         <div class="col-md-4">
                             <label class="form-label d-block" for="Input_IsPublished">발행 여부</label>
@@ -85,7 +98,7 @@
                     <div>
                         <div class="text-muted small text-uppercase mb-1">불러온 원본</div>
                         <div class="fw-semibold">@Model.Title</div>
-                        <div class="text-muted small">카테고리: @(Model.CategoryId?.ToString() ?? "미지정")</div>
+                        <div class="text-muted small">카테고리: @Model.CategoryId</div>
                         <div class="text-muted small">발행: @(Model.IsPublished ? "예" : "아니오")</div>
                     </div>
                     <article class="content-prose blog-preview-pane" data-blog-preview>@Html.Raw(Model.Content)</article>

src/TaxBaik.Web/Pages/Shared/_EmptyState.cshtml

@@ -1,4 +1,7 @@
 @model string
+@{
+    var emptyMessage = string.IsNullOrWhiteSpace(Model) ? "데이터가 없습니다." : Model;
+}
 <div class="empty py-5">
     <div class="empty-img">
         <svg xmlns="http://www.w3.org/2000/svg" class="icon icon-tabler icon-tabler-database-off" width="48" height="48" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round">
@@ -8,5 +11,5 @@
             <path d="M3 3l18 18" />
         </svg>
     </div>
-    <p class="empty-title">@string.IsNullOrWhiteSpace(Model) ? "데이터가 없습니다." : Model</p>
+    <p class="empty-title">@emptyMessage</p>
 </div>