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/Functions/ott_min_date.sql

@@ -0,0 +1,28 @@
+
+
+
+-- =============================================
+-- Author:		Dr. Stefan Ott
+-- Create date: <Create Date, ,>
+-- Description:	<Description, ,>
+-- =============================================
+CREATE FUNCTION [dbo].[ott_min_date]
+(
+	@val1 date,
+	@val2 date
+)
+RETURNS date
+AS
+BEGIN
+	DECLARE @RES date;
+	
+	IF @val1 is null and @val2 is not null
+		SET @val1 = @val2
+	IF @val2 is null and @val1 is not null
+		SET @val2 = @val1;
+
+	SELECT @RES = CASE WHEN @val1 is null and @val2 is null THEN NULL WHEN @val1 < @val2 THEN @val1 ELSE @val2 END;
+
+	RETURN @RES;
+
+END