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_Database/dbo/Stored Procedures/fds__createInvoice.sql

@@ -14,7 +14,8 @@ CREATE PROCEDURE [dbo].[fds__createInvoice]
 	@CustomerId bigint,
 	@SendToAddress nvarchar(1000),
 	@SendToEmail nvarchar(255),
-	@ProvisionPeriod varchar(50), 
+	@SendToEmailCc nvarchar(255) = NULL,
+	@ProvisionPeriod varchar(50),
 	@CustomValues nvarchar(max),
 	@authuser varchar(25),
 	@Id varchar(10) OUT,
@@ -56,6 +57,7 @@ BEGIN
 		[CustomerId] [bigint] NULL,
 		[SendToAddress] [nvarchar](1000) NULL,
 		[SendToEmail] [nvarchar](255) NULL,
+		[SendToEmailCc] [nvarchar](255) NULL,
 		[ProvisionPeriod] [varchar](50) NULL,
 		[ProvisionLocation] [nvarchar](1000) NULL,
 		[PaymentStatus] [char](1) NULL,
@@ -100,6 +102,7 @@ BEGIN
            ,[CustomerId]
            ,[SendToAddress]
            ,[SendToEmail]
+           ,[SendToEmailCc]
            ,[ProvisionPeriod]
            ,[ProvisionLocation]
 		   ,[PaymentStatus]
@@ -140,6 +143,7 @@ BEGIN
            ,@CustomerId
 		   ,@SendToAddress
            ,@SendToEmail
+           ,@SendToEmailCc
            ,@ProvisionPeriod
 		   ,NULL --[ProvisionLocation]
 		   ,NULL --[PaymentStatus]