fix(invoices): send invoice amounts as exact cent-rounded decimals

Stornorechnung saves still failed: the VAT amount was formatted invariantly
("-615.3757999999999") and re-parsed under the server's de-DE culture as
-6153757999999999, overflowing numeric(10,3) in fds__setInvoice.

- FdsInvoiceData.BuildInvoiceParams: amount params are decimal(10,x) via
  AmountParam/ParseAmount (culture-independent, rounded to cents); amounts
  beyond +/-9,999,999.99 throw InvoiceAmountOutOfRangeException.
- InvoiceService.RegisterInvoiceAsync: refuses such an invoice with a logged
  error (EventId InvoiceAmountRejected) instead of storing a wrong amount.
- Invoice editor: vat_val is cent-rounded decimal, no float noise.
- Tests: InvoiceAmountParamTests replaces the float-based Storno test.
- Bump Azure.Storage.Blobs 12.30.0; OCORE/OCORE_web submodules (AngleSharp
  1.8.3, Azure.Storage.Files.Shares 12.28.0).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Fuchs/code/FdsInvoiceData.cs

@@ -173,9 +173,9 @@ public class FdsInvoiceData
         {
             SQL_VarChar("@InvoiceType",        Admin?.nz("type") ?? ""),
             SQL_NVarChar("@InvoiceTitle",       NewValues?.nz("title") ?? ""),
-            SQL_Float("@InvoiceBalance",        stringvalue: NewValues?.nz("total_gross") ?? "0"),
-            SQL_Float("@InvoiceBalance_net",    stringvalue: NewValues?.nz("total_net") ?? "0"),
-            SQL_Float("@InvoiceVAT_net1",       stringvalue: vatNet),
+            AmountParam("@InvoiceBalance",      NewValues is null ? 0m : NewValues.getItem("total_gross"), scale: 3),
+            AmountParam("@InvoiceBalance_net",  NewValues is null ? 0m : NewValues.getItem("total_net"), scale: 3),
+            AmountParam("@InvoiceVAT_net1",     vatNet, scale: 3),
             SQL_VarChar("@InvoiceVAT_1",        vatRate),
             SQL_VarChar("@PaymentTerm",         NewValues?.nz("paymentterm") ?? "", dbNull_IfEmpty: true),
             SQL_BigInt("@CustomerId",           Admin?.nz("customerid") ?? ""),
@@ -185,12 +185,63 @@ public class FdsInvoiceData
             SQL_NVarChar("@ProvisionPeriod",    RawProvisionPeriod, dbNull_IfEmpty: true),
             SQL_NVarChar("@CustomValues",       RawCustomValues, dbNull_IfEmpty: true),
             SQL_NVarChar("@SendToAddressJson",  SendToAddressJsonForPersist(), dbNull_IfEmpty: true),
-            SQL_Float("@InvoiceService_net",    stringvalue: Sms?.nz("tscn") ?? "0"),
-            SQL_Float("@InvoiceService_VAT",    stringvalue: Sms?.nz("tscvat") ?? "0"),
+            AmountParam("@InvoiceService_net",  Sms is null ? 0m : Sms.getItem("tscn"), scale: 2),
+            AmountParam("@InvoiceService_VAT",  Sms is null ? 0m : Sms.getItem("tscvat"), scale: 2),
             SQL_VarChar("@InvoiceOptions", BuildInvoiceOptions(), dbNull_IfEmpty: true)
         };
     }
 
+    /// <summary>Largest magnitude the <c>numeric(10,x)</c> amount parameters of the invoice procs accept.</summary>
+    internal const decimal MaxAmount = 9_999_999.99m;
+
+    /// <summary>
+    /// Invoice amounts go to SQL as exact <c>decimal</c> parameters rounded to cents — never through
+    /// a culture-dependent string → float round trip. That round trip once parsed negative amounts
+    /// with the server's de-DE culture ("-615.3758" → -6153758, with float noise beyond numeric(10,3)),
+    /// so Stornorechnungen could not be saved. An amount outside the procs' range is refused here
+    /// (<see cref="InvoiceAmountOutOfRangeException"/>) instead of being stored wrongly or failing in SQL.
+    /// </summary>
+    internal static SqlParameter AmountParam(string name, object? raw, byte scale)
+    {
+        decimal? value = ParseAmount(raw);
+        if (value is { } v && Math.Abs(v) > MaxAmount)
+            throw new InvoiceAmountOutOfRangeException(name, v);
+        return new SqlParameter(name, System.Data.SqlDbType.Decimal)
+        {
+            Precision = 10,
+            Scale = scale,
+            Value = value.HasValue ? value.Value : DBNull.Value
+        };
+    }
+
+    /// <summary>
+    /// Reads an amount the draft session or editor supplied: numbers are taken as-is; strings may be
+    /// German ("-1234,56") or invariant ("-1234.56", "-1.5E-05") — a comma marks German formatting.
+    /// The result is rounded to cents. Empty / "NaN" / unparseable → null (stored as NULL).
+    /// </summary>
+    internal static decimal? ParseAmount(object? raw)
+    {
+        if (raw is JValue jv) raw = jv.Value;
+        decimal d;
+        switch (raw)
+        {
+            case null: return null;
+            case decimal m: d = m; break;
+            case double dbl when double.IsFinite(dbl): d = (decimal)dbl; break;
+            case float flt when float.IsFinite(flt): d = (decimal)flt; break;
+            case int or long or short or byte: d = Convert.ToDecimal(raw, CultureInfo.InvariantCulture); break;
+            case double or float: return null;
+            default:
+                string s = (Convert.ToString(raw, CultureInfo.InvariantCulture) ?? "").Trim();
+                var culture = s.Contains(',') ? GermanCulture : CultureInfo.InvariantCulture;
+                if (!decimal.TryParse(s, NumberStyles.Float, culture, out d)) return null;
+                break;
+        }
+        return Math.Round(d, 2, MidpointRounding.AwayFromZero);
+    }
+
+    private static readonly CultureInfo GermanCulture = new("de-DE");
+
     /// <summary>
     /// Builds the InvoiceOptions CSV from the posted admin flags.
     /// <c>§13b</c> is the existing reverse-charge flag; <c>setmode:&lt;mode&gt;</c>
@@ -253,6 +304,14 @@ public class FdsInvoiceData
     }
 }
 
+/// <summary>An invoice amount exceeds what the invoice procs' <c>numeric(10,x)</c> parameters can store.</summary>
+public sealed class InvoiceAmountOutOfRangeException(string parameter, decimal value)
+    : Exception($"Invoice amount {parameter} = {value.ToString(CultureInfo.InvariantCulture)} is outside ±{FdsInvoiceData.MaxAmount.ToString(CultureInfo.InvariantCulture)}.")
+{
+    public string Parameter { get; } = parameter;
+    public decimal Value { get; } = value;
+}
+
 /// <summary>A service-request group as it renders on the invoice: a heading plus its line items.</summary>
 public sealed class InvoiceBlock
 {