Add Fuchs_Database SSDT project (schema source of truth)

Adds the SQL Server Data Tools project for the fuchs_fds database — tables,
table types, functions and stored procedures that the backend calls (e.g.
fds__getInvoice, fds__merge_bankingtransactions, fds__tt__bankingtransactions,
fds__admin_getReportCatalog, fis_* auth). Build/model caches (bin, obj,
*.dbmdl, *.jfm, *.user) are git-ignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Fuchs_Database/dbo/Stored Procedures/backup__fds__setInvoicePayed.sql

@@ -0,0 +1,46 @@
+-- =============================================
+-- Author:		<Author,,Name>
+-- Create date: <Create Date,,>
+-- Description:	<Description,,>
+-- =============================================
+CREATE PROCEDURE [dbo].[backup__fds__setInvoicePayed]
+	@Id varchar(15),
+	@authuser varchar(25)
+AS
+BEGIN
+	SET NOCOUNT ON;
+	DECLARE @now datetime = GETUTCDATE();
+
+	IF [dbo].[fis_getModuleAuth]('fds_inv', @authuser) < 2
+		THROW 60000, N'not authorized', 1;  
+	
+	INSERT INTO [dbo].[fds__admin_activity] ([activity] ,[authuser] ,[info])
+		VALUES ('fds__setInvoicePayed' ,@authuser , (SELECT * FROM (VALUES(@Id, @authuser)) as z ([id],[authuser]) FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER));
+
+    UPDATE [dbo].[fds__invoices] SET [IsPayed] = 1, [paymentstatus] = 'm', [DateModified] = @now, [UserModified] = @authuser, [version] = (ISNULL([version],0) + 1)
+	OUTPUT inserted.*
+		WHERE [Id] = @Id AND @Id is not null and [IsPayed] = 0;
+
+	IF TRY_CAST(@id as bigint) is not null and EXISTS(SELECT 0 FROM [dbo].[mfr__invoices] as i where i.[id] = TRY_CAST(@id as bigint))
+		BEGIN
+			MERGE [dbo].[fds__custom_invoiceinfo] as TARGET
+			USING (VALUES
+					   (TRY_CAST(@id as bigint)
+					   ,CAST('m' as char(1))
+					   ,CAST(1 as bit))) as SOURCE([InvId],[PaymentStatus],[isPayed]) 
+					ON TARGET.[InvID] = SOURCE.[InvID]
+			WHEN MATCHED THEN
+				UPDATE SET TARGET.[PaymentStatus] = SOURCE.[PaymentStatus]
+					,TARGET.[isPayed] = SOURCE.[isPayed]
+			WHEN NOT MATCHED THEN 
+				INSERT ([InvId],[PaymentStatus],[isPayed],[file])
+				VALUES(
+					SOURCE.[InvId]
+					,SOURCE.[PaymentStatus]
+					,SOURCE.[isPayed]
+					,NULL
+				);
+
+		END
+
+END