feat(1099): round-trip Form1099BoxId through expense category DTOs/service

Mirror Form990LineId: add Form1099BoxId + Form1099BoxCode to all four
category DTOs (response + request, group + sub); load a boxCodes lookup
dictionary in GetAllAsync and project it; set/copy the field in
CreateGroupAsync, UpdateGroupAsync, CreateSubCategoryAsync, and
UpdateSubCategoryAsync. All 4 category-service unit tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API/ROLAC.API/DTOs/Expense/ExpenseCategoryDtos.cs

@@ -11,6 +11,8 @@ public class ExpenseSubCategoryDto
     public bool    IsActive  { get; set; }
     public int?    Form990LineId   { get; set; }
     public string? Form990LineCode { get; set; }
+    public int?    Form1099BoxId   { get; set; }
+    public string? Form1099BoxCode { get; set; }
 }
 
 public class ExpenseCategoryGroupDto
@@ -22,6 +24,8 @@ public class ExpenseCategoryGroupDto
     public bool    IsActive  { get; set; }
     public int?    Form990LineId   { get; set; }
     public string? Form990LineCode { get; set; }
+    public int?    Form1099BoxId   { get; set; }
+    public string? Form1099BoxCode { get; set; }
     public List<ExpenseSubCategoryDto> SubCategories { get; set; } = [];
 }
 
@@ -31,6 +35,7 @@ public class CreateExpenseGroupRequest
     [MaxLength(200)] public string? Name_zh { get; set; }
     public int SortOrder { get; set; }
     public int? Form990LineId { get; set; }
+    public int? Form1099BoxId { get; set; }
 }
 public class UpdateExpenseGroupRequest : CreateExpenseGroupRequest
 {
@@ -44,6 +49,7 @@ public class CreateExpenseSubCategoryRequest
     [MaxLength(200)] public string? Name_zh { get; set; }
     public int SortOrder { get; set; }
     public int? Form990LineId { get; set; }
+    public int? Form1099BoxId { get; set; }
 }
 public class UpdateExpenseSubCategoryRequest : CreateExpenseSubCategoryRequest
 {

API/ROLAC.API/Services/ExpenseCategoryService.cs

@@ -25,25 +25,32 @@ public class ExpenseCategoryService : IExpenseCategoryService
         var lineCodes = await _db.Form990ExpenseLines.AsNoTracking()
             .ToDictionaryAsync(l => l.Id, l => l.LineCode);
 
+        var boxCodes = await _db.Form1099Boxes.AsNoTracking()
+            .ToDictionaryAsync(b => b.Id, b => b.BoxCode);
+
         return groups.Select(g => new ExpenseCategoryGroupDto
         {
             Id = g.Id, Name_en = g.Name_en, Name_zh = g.Name_zh,
             SortOrder = g.SortOrder, IsActive = g.IsActive,
             Form990LineId   = g.Form990LineId,
             Form990LineCode = g.Form990LineId.HasValue ? lineCodes.GetValueOrDefault(g.Form990LineId.Value) : null,
+            Form1099BoxId   = g.Form1099BoxId,
+            Form1099BoxCode = g.Form1099BoxId.HasValue ? boxCodes.GetValueOrDefault(g.Form1099BoxId.Value) : null,
             SubCategories = subs.Where(s => s.GroupId == g.Id).Select(s => new ExpenseSubCategoryDto
             {
                 Id = s.Id, GroupId = s.GroupId, Name_en = s.Name_en, Name_zh = s.Name_zh,
                 SortOrder = s.SortOrder, IsActive = s.IsActive,
                 Form990LineId   = s.Form990LineId,
                 Form990LineCode = s.Form990LineId.HasValue ? lineCodes.GetValueOrDefault(s.Form990LineId.Value) : null,
+                Form1099BoxId   = s.Form1099BoxId,
+                Form1099BoxCode = s.Form1099BoxId.HasValue ? boxCodes.GetValueOrDefault(s.Form1099BoxId.Value) : null,
             }).ToList(),
         }).ToList();
     }
 
     public async Task<int> CreateGroupAsync(CreateExpenseGroupRequest r)
     {
-        var g = new ExpenseCategoryGroup { Name_en = r.Name_en, Name_zh = r.Name_zh, SortOrder = r.SortOrder, IsActive = true, Form990LineId = r.Form990LineId };
+        var g = new ExpenseCategoryGroup { Name_en = r.Name_en, Name_zh = r.Name_zh, SortOrder = r.SortOrder, IsActive = true, Form990LineId = r.Form990LineId, Form1099BoxId = r.Form1099BoxId };
         _db.ExpenseCategoryGroups.Add(g);
         await _db.SaveChangesAsync();
         return g.Id;
@@ -53,7 +60,7 @@ public class ExpenseCategoryService : IExpenseCategoryService
     {
         var g = await _db.ExpenseCategoryGroups.FindAsync(id)
             ?? throw new KeyNotFoundException($"ExpenseCategoryGroup {id} not found.");
-        g.Name_en = r.Name_en; g.Name_zh = r.Name_zh; g.SortOrder = r.SortOrder; g.IsActive = r.IsActive; g.Form990LineId = r.Form990LineId;
+        g.Name_en = r.Name_en; g.Name_zh = r.Name_zh; g.SortOrder = r.SortOrder; g.IsActive = r.IsActive; g.Form990LineId = r.Form990LineId; g.Form1099BoxId = r.Form1099BoxId;
         await _db.SaveChangesAsync();
     }
 
@@ -69,7 +76,7 @@ public class ExpenseCategoryService : IExpenseCategoryService
     {
         var exists = await _db.ExpenseCategoryGroups.AnyAsync(g => g.Id == r.GroupId);
         if (!exists) throw new KeyNotFoundException($"ExpenseCategoryGroup {r.GroupId} not found.");
-        var s = new ExpenseSubCategory { GroupId = r.GroupId, Name_en = r.Name_en, Name_zh = r.Name_zh, SortOrder = r.SortOrder, IsActive = true, Form990LineId = r.Form990LineId };
+        var s = new ExpenseSubCategory { GroupId = r.GroupId, Name_en = r.Name_en, Name_zh = r.Name_zh, SortOrder = r.SortOrder, IsActive = true, Form990LineId = r.Form990LineId, Form1099BoxId = r.Form1099BoxId };
         _db.ExpenseSubCategories.Add(s);
         await _db.SaveChangesAsync();
         return s.Id;
@@ -79,7 +86,7 @@ public class ExpenseCategoryService : IExpenseCategoryService
     {
         var s = await _db.ExpenseSubCategories.FindAsync(id)
             ?? throw new KeyNotFoundException($"ExpenseSubCategory {id} not found.");
-        s.GroupId = r.GroupId; s.Name_en = r.Name_en; s.Name_zh = r.Name_zh; s.SortOrder = r.SortOrder; s.IsActive = r.IsActive; s.Form990LineId = r.Form990LineId;
+        s.GroupId = r.GroupId; s.Name_en = r.Name_en; s.Name_zh = r.Name_zh; s.SortOrder = r.SortOrder; s.IsActive = r.IsActive; s.Form990LineId = r.Form990LineId; s.Form1099BoxId = r.Form1099BoxId;
         await _db.SaveChangesAsync();
     }