feat(expense-categories): AI 建議 for group/sub name + 990 line

Add an AI assist button to the Edit/New Group (大項) and Subcategory
(小項) dialogs: the user enters a Chinese name, and the model refines
the Chinese, translates it to English, and suggests the matching IRS
Form 990 Part IX line. Suggestions surface in a confirm card; Apply
fills the Chinese name, English name, and 990 line fields.

Backend mirrors the existing expense-classification AI family but over
the Form 990 line catalog: IExpenseCategoryAiService + base (catalog
load, prompt, id validation) + Claude/Gemini providers + factory that
picks the provider from ChurchProfile.AiProvider. New write-gated
POST api/expense-categories/ai-suggest endpoint; sub-category requests
pass the parent group + its 990 line to bias the choice.

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

API/ROLAC.API/Program.cs

@@ -190,6 +190,12 @@ builder.Services.AddScoped<ROLAC.API.Services.Ai.IChurchAiConfigProvider,
 builder.Services.AddScoped<ROLAC.API.Services.Ai.IExpenseAiServiceFactory,
                            ROLAC.API.Services.Ai.ExpenseAiServiceFactory>();
 
+// Category-mapping AI (define a 大項/小項: refine name + translate + suggest Form 990 line).
+builder.Services.AddHttpClient<ROLAC.API.Services.Ai.GeminiExpenseCategoryAiService>();
+builder.Services.AddHttpClient<ROLAC.API.Services.Ai.ClaudeExpenseCategoryAiService>();
+builder.Services.AddScoped<ROLAC.API.Services.Ai.IExpenseCategoryAiServiceFactory,
+                           ROLAC.API.Services.Ai.ExpenseCategoryAiServiceFactory>();
+
 // ---------------------------------------------------------------------------
 // Configurable role-based permissions (RBAC matrix)
 // ---------------------------------------------------------------------------