Add Cc (Zusatzempfänger) recipient support for invoice emails

Lets an invoice carry an additional Cc recipient alongside the primary
SendToEmail, sent via the ProcessWeb mailer API. Honors the
Fuchs:Email:OverrideRecipient dev safety net: when the override is
active, Cc is dropped entirely (only the single override inbox is
ever reached), never leaked to it.

- IComService.SendEmailAsync / ProcessWebComService: new optional
  `cc` parameter, included in the mailer payload only when non-empty.
- FdsInvoiceData.RawInvoiceEmailCc + BuildInvoiceParams: reads
  `new.invoiceemailcc`, posts @SendToEmailCc.
- IntranetController.Requests: reads SendToEmailCc from the loaded
  invoice row and passes it through on send/resend.
- Fuchs_Database: SendToEmailCc column on fds__invoices, threaded
  through fds__createInvoice/fds__setInvoice/fds__getInvoice and the
  fds__tt__invoice_base/_core table types.
- fis.req_txt_de.js: "Zusatzempfänger (CC)" field label.
- Tests: ProcessWebComServiceTests (Cc included/omitted/dropped under
  override); SystemStatusServiceTests mocks updated for the new
  IComService.SendEmailAsync parameter.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Fuchs.Tests/ProcessWebComServiceTests.cs

@@ -322,6 +322,46 @@ public class ProcessWebComServiceTests
         Assert.Equal("realcustomer@example.de", json["communication"]!["to"]!.ToString());
     }
 
+    // ── Cc recipient ("Zusatzempfänger") ─────────────────────────────────────────
+    [Fact]
+    public async Task SendEmailAsync_CcProvided_IsIncludedInPayload()
+    {
+        var handler = new StubHandler(HttpStatusCode.OK);
+        var svc = CreateService(handler);
+
+        await svc.SendEmailAsync("inv_cc1", "Subject", "<p>hi</p>", "kunde@example.de", "Kunde",
+            cc: "zusatz@example.de");
+
+        var json = JObject.Parse(handler.LastRequestBody!);
+        Assert.Equal("zusatz@example.de", json["communication"]!["cc"]!.ToString());
+    }
+
+    [Fact]
+    public async Task SendEmailAsync_CcOmitted_IsNullInPayload()
+    {
+        var handler = new StubHandler(HttpStatusCode.OK);
+        var svc = CreateService(handler);
+
+        await svc.SendEmailAsync("inv_cc2", "Subject", "<p>hi</p>", "kunde@example.de", "Kunde");
+
+        var json = JObject.Parse(handler.LastRequestBody!);
+        Assert.Equal(JTokenType.Null, json["communication"]!["cc"]!.Type);
+    }
+
+    [Fact]
+    public async Task SendEmailAsync_OverrideRecipientSet_DropsCcEntirely()
+    {
+        var handler = new StubHandler(HttpStatusCode.OK);
+        var svc = CreateService(handler, overrideRecipient: "dev-inbox@example.test");
+
+        await svc.SendEmailAsync("inv_cc3", "Subject", "<p>hi</p>", "realcustomer@example.de", "Kunde",
+            cc: "zusatz@example.de");
+
+        var json = JObject.Parse(handler.LastRequestBody!);
+        Assert.Equal("dev-inbox@example.test", json["communication"]!["to"]!.ToString());
+        Assert.Equal(JTokenType.Null, json["communication"]!["cc"]!.Type);
+    }
+
     // ── Override enforcement across every real appsettings*.json environment ───
     // Loads the ACTUAL Fuchs/appsettings*.json files the same way ASP.NET Core
     // layers them (base file + optional environment-specific overlay). These files

Fuchs.Tests/SystemStatusServiceTests.cs

@@ -404,7 +404,7 @@ public class SystemStatusServiceTests
 
         Assert.False(r.Sent);
         com.Verify(c => c.SendEmailAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
-            It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>>()), Times.Never);
+            It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>>(), It.IsAny<string?>()), Times.Never);
     }
 
     [Fact]
@@ -413,9 +413,9 @@ public class SystemStatusServiceTests
         string? capturedHtml = null, capturedTo = null, capturedSubject = null;
         var com = new Mock<IComService>();
         com.Setup(c => c.SendEmailAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
-                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>()))
-            .Callback<string, string, string, string, string, Dictionary<string, byte[]>?>(
-                (_, subj, html, to, _, _) => { capturedSubject = subj; capturedHtml = html; capturedTo = to; })
+                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>(), It.IsAny<string?>()))
+            .Callback<string, string, string, string, string, Dictionary<string, byte[]>?, string?>(
+                (_, subj, html, to, _, _, _) => { capturedSubject = subj; capturedHtml = html; capturedTo = to; })
             .ReturnsAsync(true);
         var svc = Build(com: com);
 
@@ -436,7 +436,7 @@ public class SystemStatusServiceTests
     {
         var com = new Mock<IComService>();
         com.Setup(c => c.SendEmailAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
-                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>()))
+                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>(), It.IsAny<string?>()))
             .ReturnsAsync(true);
         var svc = Build(com: com, email: new FuchsEmailSettings { OverrideRecipient = "safety@example.test" });
 
@@ -453,7 +453,7 @@ public class SystemStatusServiceTests
     {
         var com = new Mock<IComService>();
         com.Setup(c => c.SendEmailAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(),
-                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>()))
+                It.IsAny<string>(), It.IsAny<string>(), It.IsAny<Dictionary<string, byte[]>?>(), It.IsAny<string?>()))
             .ReturnsAsync(false);
         var svc = Build(com: com);