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/fds__setInvoiceUNPayed.sql

@@ -0,0 +1,37 @@
+-- =============================================
+-- Author:		<Author,,Name>
+-- Create date: <Create Date,,>
+-- Description:	<Description,,>
+-- =============================================
+CREATE PROCEDURE [dbo].[fds__setInvoiceUNPayed]
+	@Id varchar(8),
+	@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__setInvoiceUNPayed' ,@authuser , (SELECT * FROM (VALUES(@Id, @authuser)) as z ([id],[authuser]) FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER));
+
+	IF EXISTS (SELECT 0 FROM [dbo].[fds__invoices] WHERE [Id] = @Id 
+			AND @Id is not null
+			AND [PaymentStatus] = 'm')
+		BEGIN
+
+			UPDATE [dbo].[fds__invoices] 
+			SET [IsPayed] = 0, [paymentstatus] = NULL, [DateModified] = @now, [UserModified] = @authuser, [version] = (ISNULL([version],0) + 1)
+			OUTPUT inserted.*
+				WHERE [Id] = @Id 
+					AND @Id is not null
+					AND [PaymentStatus] = 'm';
+
+			--apply auto status
+			EXECUTE [dbo].[fds__setInvoicePaymentStatus_auto_single] @Id;
+
+		END
+
+END