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/mfr__invoices.sql

@@ -0,0 +1,27 @@
+CREATE TABLE [dbo].[mfr__invoices] (
+    [Id]                   BIGINT           NOT NULL,
+    [Version]              INT              NOT NULL,
+    [DateOfCreation]       DATETIME         NOT NULL,
+    [URI]                  NVARCHAR (255)   NULL,
+    [DocumentName]         NVARCHAR (255)   NULL,
+    [ReportDefinitionCode] NVARCHAR (255)   NULL,
+    [FileType]             NVARCHAR (255)   NULL,
+    [InvoiceBalance]       NUMERIC (10, 3)  NULL,
+    [InvoiceBalanceNetto]  NUMERIC (10, 3)  NULL,
+    [WageBalanceNet]       NUMERIC (10, 3)  NULL,
+    [DatePayed]            DATETIME         NULL,
+    [InvoiceId]            NVARCHAR (50)    NULL,
+    [DueDate]              DATETIME         NOT NULL,
+    [WithoutVAT]           BIT              NOT NULL,
+    [Skonto]               NUMERIC (10, 3)  NOT NULL,
+    [PartialPayment]       NUMERIC (10, 3)  NULL,
+    [InvoiceState]         NVARCHAR (255)   NULL,
+    [Note]                 NVARCHAR (MAX)   NULL,
+    [file_guid]            UNIQUEIDENTIFIER CONSTRAINT [DF_mfr__invoices_file_guid] DEFAULT (newid()) NULL
+);
+
+
+GO
+CREATE NONCLUSTERED INDEX [mfr__invoices__ix1]
+    ON [dbo].[mfr__invoices]([Id] ASC, [InvoiceId] ASC);
+