Add invoice provision-period PDF handling

Normalize invoice provision periods in PDF generation, switch admin labels between single-date and range modes, add end-to-end tests, update package and frontend bundle versions, and note the invoice lifecycle docs update.

Fuchs/Docs/INVOICE_LIFECYCLE.md

@@ -97,7 +97,9 @@ payload; see `EVAL_live_invoice_editing.md` for the rationale.
   it drives the EN 16931 eRechnung and composes the free-text `SendToAddress` for the
   PDF (see [`Concepts/erechnung-output.md`](Concepts/erechnung-output.md)). The **service
   date/period** (Leistungsdatum/-zeitraum) is likewise a structured German-date dialog
-  (`$inv.eProvisionPeriod`) — a single date or a from/to range — mapped to BT-72 / BG-14.
+  (`$inv.eProvisionPeriod`) — a single date or a from/to range — mapped to BT-72 / BG-14
+  and printed in the PDF's admin block (`InvoiceService.ApplyProvisionPeriod`; legacy ISO
+  values are shown as German dates).
 - **§13b reverse-charge** toggle (`$inv.sp13b`) — suppresses VAT lines/columns.
 - **Set-pricing display mode** (`$inv.ssetmode` / `setSetmode`) — `SetPrice`
   (default) / `SetOnly`; see `INVOICE_SET_PRICING.md`. Purely presentational

Fuchs/Fuchs.csproj

@@ -51,10 +51,10 @@
     <PackageReference Include="Newtonsoft.Json" Version="13.0.4" />
     <!-- New packages (needed for .NET 10) -->
     <PackageReference Include="Microsoft.Data.SqlClient" Version="7.1.1" />
-    <PackageReference Include="SixLabors.ImageSharp" Version="4.1.2" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="4.1.3" />
     <PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.12" />
     <PackageReference Include="System.Drawing.Common" Version="10.0.12" />
-    <PackageReference Include="Azure.Storage.Blobs" Version="12.30.0" />
+    <PackageReference Include="Azure.Storage.Blobs" Version="12.30.1" />
   </ItemGroup>
   <ItemGroup>
     <Folder Include="App_Data\cache\" />

Fuchs/Services/InvoiceService.cs

@@ -320,6 +320,22 @@ public class InvoiceService : IInvoiceService
         }
     }
 
+    /// <summary>
+    /// Puts the stored Leistungsdatum / -zeitraum into the PDF admin block: German dates (legacy ISO
+    /// values converted) and the label the editor shows — "Leistungsdatum" for one date,
+    /// "Leistungszeitraum" for a from–to range.
+    /// </summary>
+    internal static void ApplyProvisionPeriod(FuchsPdf.FdsTextBlocks tb, string? provisionPeriod)
+    {
+        tb.ProvisionPeriod = ProvisionPeriodForDisplay(provisionPeriod).Trim();
+        tb.AdminProvLabel  = tb.ProvisionPeriod.Contains(" - ") || tb.ProvisionPeriod.Length == 0
+            ? "Leistungszeitraum" : "Leistungsdatum";
+    }
+
+    /// <summary>Shows ISO dates (yyyy-MM-dd) saved by older editor versions as German dd.MM.yyyy.</summary>
+    internal static string ProvisionPeriodForDisplay(string? period) =>
+        System.Text.RegularExpressions.Regex.Replace(period ?? "", @"\b(\d{4})-(\d{2})-(\d{2})\b", "$3.$2.$1");
+
     public async Task<Document> GenerateInvoicePdfAsync(FdsInvoiceData invoice, bool draft)
     {
         using var act = FuchsTelemetry.StartActivity("invoice.render");
@@ -339,6 +355,7 @@ public class InvoiceService : IInvoiceService
             // e-invoice issue date (ERechnungMapper), see InvoiceDates / ADR 0032.
             AdminDatumValue = InvoiceDates.IssueDate(reg).ToDateTime(TimeOnly.MinValue)
         };
+        ApplyProvisionPeriod(tb, reg?.getString("ProvisionPeriod"));
         var inlineImages = await ResolveInlineImagesAsync(invoice);
         var doc = await _pdf.WriteLetterAsync(tb, draft);
         doc.Info.Title = reg?.getString("InvoiceTitle") ?? "";