Show signed amounts on the transactions page and in its charts

Adds TransactionDataset.GetValue(bool, string accountId), which
negates the value when the given account is the transaction's origin
(paying out) so the account's own transaction list and charts show
a minus sign for outgoing money, regardless of account class. Removes
the old Activa-only sign flip baked into
ViewService.GetTransactionViewListAsync(accountId), which would have
double-negated Activa bookings against the new accountId-aware
GetValue. ChartService's booking-text totals now sum through the same
accountId-aware GetValue instead of filtering to inbound transactions
only, so a booking text nets its in/out transactions correctly.

Schaad.Accounting.Common/Datasets/TransactionDataset.cs

@@ -33,5 +33,15 @@ namespace Schaad.Accounting.Datasets
             else
                 return Value;
         }
+
+        public decimal GetValue(bool withFxRate, string accountId)
+        {
+            if (accountId == OriginAccountId)
+            {
+                return -1 * GetValue(withFxRate);
+            }
+
+            return GetValue(withFxRate);
+        }
     }
 }

Schaad.Accounting.Services/ChartService.cs

@@ -112,7 +112,7 @@ namespace Schaad.Accounting.Services
             {
                 var groupedByMonth = grp
                     .GroupBy(t => t.ValueDate.Month)
-                    .ToDictionary(g => g.Key, g => g.Sum(t => t.GetValue(account.IsFxAccount)));
+                    .ToDictionary(g => g.Key, g => g.Sum(t => t.GetValue(account.IsFxAccount, accountId)));
                 EnsureEntryForEveryMonth(groupedByMonth, maxMonth);
 
                 list.Add(new DataSerie(
@@ -132,7 +132,7 @@ namespace Schaad.Accounting.Services
 
             return transactions
                 .GroupBy(t => t.Text)
-                .Select(g => new CategoryTotal(g.Key, g.Sum(t => t.GetValue(account.IsFxAccount))))
+                .Select(g => new CategoryTotal(g.Key, g.Sum(t => t.GetValue(account.IsFxAccount, accountId))))
                 .Where(c => c.Value != 0)
                 .ToList();
         }

Schaad.Accounting.Services/ViewService.cs

@@ -132,8 +132,9 @@ namespace Schaad.Accounting.Services
         }
 
         /// <summary>
-        /// Get transaction list filtered to a single account, with values sign-flipped
+        /// Get transaction list filtered to a single account. Sign is not baked in here -
-        /// when the requested account is the origin of an activa booking.
+        /// callers use <see cref="TransactionDataset.GetValue(bool, string)"/> with this
+        /// account's id to get a value that's negative when the account is paying out.
         /// </summary>
         public async Task<List<TransactionDataset>> GetTransactionViewListAsync(string accountId)
         {
@@ -143,22 +144,10 @@ namespace Schaad.Accounting.Services
 
             return transactionList.Select(t =>
                     new TransactionDataset(
-                        WithDisplaySign(t),
+                        t,
                         accountsById[t.OriginAccountId],
                         accountsById[t.TargetAccountId]))
                 .ToList();
-
-            Transaction WithDisplaySign(Transaction t)
-            {
-                var originAccount = accountsById[t.OriginAccountId];
-                if (originAccount.Class == ClassIds.Activa && accountId == t.OriginAccountId)
-                {
-                    var copy = t.Clone();
-                    copy.Value *= -1;
-                    return copy;
-                }
-                return t;
-            }
         }
 
         /// <summary>

Schaad.Accounting.Tests/ChartServiceTestShould.cs

@@ -186,11 +186,27 @@ public class ChartServiceTestShould
 
         series.Count.ShouldBe(2);
         var migros = series.Single(s => s.Name == "Migros");
-        migros.Y[0].ShouldBe(50m);
+        migros.Y[0].ShouldBe(-50m);
         migros.Y[1].ShouldBe(0m);
         var coop = series.Single(s => s.Name == "Coop");
         coop.Y[0].ShouldBe(0m);
-        coop.Y[1].ShouldBe(20m);
+        coop.Y[1].ShouldBe(-20m);
+    }
+
+    [Fact]
+    public async Task ShowPositiveValueWhenAccountIsTargetOfBookingTextTransaction()
+    {
+        var checking = MakeAccount("chk", 1010);
+        var salary = MakeAccount("sal", 3000);
+        viewService.GetAccountViewAsync("chk").Returns(AsDataset(checking));
+        viewService.GetTransactionViewListAsync("chk").Returns(new List<TransactionDataset>
+        {
+            MakeTransaction(salary, checking, value: 5000m, valueDate: new DateTime(2026, 1, 5), text: "Lohn")
+        });
+
+        var series = await BuildService().GetBookingTextExpensesPerMonthAsync("chk");
+
+        series.Single().Y.Single().ShouldBe(5000m);
     }
 
     [Fact]
@@ -206,7 +222,7 @@ public class ChartServiceTestShould
 
         var series = await BuildService().GetBookingTextExpensesPerMonthAsync("chk");
 
-        series.Single().Y.Single().ShouldBe(200m);
+        series.Single().Y.Single().ShouldBe(-200m);
     }
 
     [Fact]
@@ -225,8 +241,25 @@ public class ChartServiceTestShould
         var totals = await BuildService().GetBookingTextTotalsAsync("chk");
 
         totals.Count.ShouldBe(2);
-        totals.ShouldContain(t => t.Name == "Migros" && t.Value == 80m);
+        totals.ShouldContain(t => t.Name == "Migros" && t.Value == -80m);
-        totals.ShouldContain(t => t.Name == "Coop" && t.Value == 20m);
+        totals.ShouldContain(t => t.Name == "Coop" && t.Value == -20m);
+    }
+
+    [Fact]
+    public async Task NetOutgoingAndIncomingBookingsWithTheSameTextWhenBuildingTotalsForAccount()
+    {
+        var checking = MakeAccount("chk", 1010);
+        var groceries = MakeAccount("groc", 4200);
+        viewService.GetAccountViewAsync("chk").Returns(AsDataset(checking));
+        viewService.GetTransactionViewListAsync("chk").Returns(new List<TransactionDataset>
+        {
+            MakeTransaction(checking, groceries, value: 50m, valueDate: new DateTime(2026, 1, 5), text: "Migros"),
+            MakeTransaction(groceries, checking, value: 20m, valueDate: new DateTime(2026, 1, 6), text: "Migros")
+        });
+
+        var totals = await BuildService().GetBookingTextTotalsAsync("chk");
+
+        totals.Single().Value.ShouldBe(-30m);
     }
 
     [Fact]

Schaad.Accounting.Tests/TransactionDatasetTestShould.cs

@@ -0,0 +1,54 @@
+using Schaad.Accounting.Datasets;
+using Schaad.Accounting.Models;
+using Shouldly;
+
+namespace Schaad.Accounting.Tests;
+
+public class TransactionDatasetTestShould
+{
+    private static Account MakeAccount(string id) => new() { Id = id, Name = id, Currency = "CHF" };
+
+    private static TransactionDataset MakeTransaction(Account origin, Account target, decimal value, decimal? fxRate = null) =>
+        new(
+            new Transaction
+            {
+                Id = Guid.NewGuid().ToString(),
+                OriginAccountId = origin.Id,
+                TargetAccountId = target.Id,
+                Value = value,
+                FxRate = fxRate,
+                ValueDate = DateTime.Now,
+                BookingDate = DateTime.Now
+            },
+            origin, target);
+
+    [Fact]
+    public void ReturnNegativeValueWhenAccountIsOrigin()
+    {
+        var checking = MakeAccount("chk");
+        var groceries = MakeAccount("groc");
+        var transaction = MakeTransaction(checking, groceries, value: 50m);
+
+        transaction.GetValue(withFxRate: false, accountId: "chk").ShouldBe(-50m);
+    }
+
+    [Fact]
+    public void ReturnPositiveValueWhenAccountIsTarget()
+    {
+        var checking = MakeAccount("chk");
+        var groceries = MakeAccount("groc");
+        var transaction = MakeTransaction(groceries, checking, value: 50m);
+
+        transaction.GetValue(withFxRate: false, accountId: "chk").ShouldBe(50m);
+    }
+
+    [Fact]
+    public void ApplyFxConversionBeforeApplyingSignWhenAccountIsOrigin()
+    {
+        var checking = MakeAccount("chk");
+        var groceries = MakeAccount("groc");
+        var transaction = MakeTransaction(checking, groceries, value: 100m, fxRate: 0.5m);
+
+        transaction.GetValue(withFxRate: true, accountId: "chk").ShouldBe(-200m);
+    }
+}

Schaad.Accounting.UI/Components/Pages/Transactions.razor

@@ -62,7 +62,7 @@
                     @GetAccountName(context)
                 </TemplateColumn>
                 <TemplateColumn Title="Betrag" Align="Align.End">
-                    @context.GetValue(selectedAccount.IsFxAccount).ToString("N2") @selectedAccount.Currency
+                    @context.GetValue(selectedAccount.IsFxAccount, selectedAccountId).ToString("N2") @selectedAccount.Currency
                 </TemplateColumn>
                 <TemplateColumn Align="Align.Center" Width="50px">
                     <FluentButton IconEnd="@(new Icons.Regular.Size16.Delete())" Appearance="Appearance.Neutral" title="Löschen" aria-label="Löschen" OnClick="@(() => DeleteAsync(context.Id))"/>