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_details.sql

@@ -0,0 +1,11 @@
+CREATE TABLE [dbo].[fds__invoice_details] (
+    [InvId]              VARCHAR (10)    NOT NULL,
+    [InvoiceService_net] NUMERIC (10, 2) NULL,
+    [InvoiceService_VAT] NUMERIC (10, 2) NULL,
+    [AllocatedTo_InvId]  VARCHAR (10)    NULL,
+    [StornoTo_InvId]     VARCHAR (20)    NULL,
+    [InvoiceOptions]     VARCHAR (50)    NULL,
+    [log]                VARCHAR (MAX)   NULL,
+    CONSTRAINT [PK_fds__invoice_details] PRIMARY KEY CLUSTERED ([InvId] ASC)
+);
+