fix(expense-snapshot): validate functional class + stamp DeletedBy on soft delete

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

API/ROLAC.API/Services/ExpenseSnapshotService.cs

@@ -1,3 +1,5 @@
+using System.Security.Claims;
+using Microsoft.AspNetCore.Http;
 using Microsoft.EntityFrameworkCore;
 using ROLAC.API.Data;
 using ROLAC.API.DTOs.Expense;
@@ -8,7 +10,17 @@ namespace ROLAC.API.Services;
 public class ExpenseSnapshotService : IExpenseSnapshotService
 {
     private readonly AppDbContext _db;
-    public ExpenseSnapshotService(AppDbContext db) => _db = db;
+    private readonly IHttpContextAccessor _http;
+    public ExpenseSnapshotService(AppDbContext db, IHttpContextAccessor http)
+    { _db = db; _http = http; }
+
+    // The JWT carries the user id in the "sub" claim (NameClaimType="sub", MapInboundClaims=false),
+    // so ClaimTypes.NameIdentifier is absent at runtime. Check NameIdentifier first (unit tests set it),
+    // then fall back to "sub" (real tokens). Required for the self-ownership guard to work in production.
+    private string CurrentUserId =>
+        _http.HttpContext?.User.FindFirstValue(ClaimTypes.NameIdentifier)
+        ?? _http.HttpContext?.User.FindFirstValue("sub")
+        ?? "system";
 
     public async Task<List<ExpenseSnapshotDto>> GetAllAsync()
     {
@@ -101,7 +113,7 @@ public class ExpenseSnapshotService : IExpenseSnapshotService
     {
         var s = await _db.ExpenseSnapshots.FirstOrDefaultAsync(x => x.Id == id)
             ?? throw new KeyNotFoundException($"Snapshot {id} not found.");
-        s.IsDeleted = true; s.DeletedAt = DateTimeOffset.UtcNow;
+        s.IsDeleted = true; s.DeletedAt = DateTimeOffset.UtcNow; s.DeletedBy = CurrentUserId;
         await _db.SaveChangesAsync();
     }
 
@@ -115,6 +127,8 @@ public class ExpenseSnapshotService : IExpenseSnapshotService
                 throw new InvalidOperationException("Each snapshot line needs a category group and subcategory.");
             if (l.Amount <= 0)
                 throw new InvalidOperationException("Each snapshot line amount must be greater than zero.");
+            if (l.FunctionalClass is not null && !FunctionalClasses.All.Contains(l.FunctionalClass))
+                throw new InvalidOperationException($"Invalid functional class '{l.FunctionalClass}'.");
         }
     }