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/fis_admin_getUserAuth.sql

@@ -0,0 +1,23 @@
+-- =============================================
+-- Author:		<Author,,Name>
+-- Create date: <Create Date, ,>
+-- Description:	<Description, ,>
+-- =============================================
+CREATE FUNCTION [dbo].[fis_admin_getUserAuth]
+(
+	@useraccount_id varchar(5)
+)
+RETURNS smallint
+AS
+BEGIN
+	DECLARE @auth smallint = -1;
+
+	SET @auth =	 ISNULL((SELECT TOP(1) 
+						ISNULL(TRY_CAST((SELECT TOP(1) [value] FROM [fis_useraccounts_settings] as s WHERE s.[useraccount_id] = ua.[useraccount_id] and s.[key] = 'intranet_admin') as smallint),	CASE WHEN [useraccount_id] is null THEN -1 WHEN [DateDisabled] is not null THEN 0 ELSE 1 END  )
+						FROM [dbo].[fis_useraccounts] as ua
+						WHERE ua.[DateDeleted] is null
+							AND ua.[useraccount_id] = @useraccount_id), -1);
+
+	RETURN @auth;
+
+END