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/Tables/fds__invoice_items.sql

@@ -0,0 +1,23 @@
+CREATE TABLE [dbo].[fds__invoice_items] (
+    [Id]              BIGINT          IDENTITY (1, 1) NOT NULL,
+    [InvId]           VARCHAR (10)    NOT NULL,
+    [InvRqId]         VARCHAR (10)    NOT NULL,
+    [mfr__item]       BIGINT          NULL,
+    [reference_InvId] VARCHAR (20)    NULL,
+    [Type]            NVARCHAR (255)  NULL,
+    [Position]        VARCHAR (5)     NULL,
+    [Quantity]        NVARCHAR (25)   NULL,
+    [Text]            NVARCHAR (MAX)  NULL,
+    [value]           NUMERIC (10, 2) NULL,
+    [value_total]     NUMERIC (10, 2) NULL,
+    [vat]             NUMERIC (5, 2)  NULL,
+    [value_service]   NUMERIC (10, 2) NULL,
+    [det]             BIT             NULL,
+    [SortOrder]       TINYINT         NOT NULL
+);
+
+
+GO
+CREATE NONCLUSTERED INDEX [fds__invoice_items__ix1]
+    ON [dbo].[fds__invoice_items]([InvId] ASC);
+