Add unit tests for Fuchs_DataService and related components

- Introduced comprehensive unit tests for the Fuchs_DataService library, covering DATEV header formatting, CSV/XML generation, and FdsMfrClient construction.
- Implemented tests for FdsMfr.UpdateNeed parsing and FdsShared utility helpers, ensuring correct functionality and stability.
- Added tests for FdsConfig and FdsMfrClient to validate configuration resolution and client construction.

Document decisions on backend-authoritative invoice and reminder handling

- Created ADR 0008 to clarify that all invoice types and reminder stages are backend-authoritative during drafting and previewing.
- Established that all calculations and settings must be processed server-side, ensuring consistency between online editor and PDF outputs.

Define irreversible mutations for set-price modes in invoices

- Documented ADR 0009 to specify that the "Set mit Preis" and "Nur Set mit Preis" operations are irreversible mutations affecting service request blocks.
- Clarified that these operations are not display toggles but actual data changes, ensuring clear expectations for invoice handling.

Transition MFR ERP sync to in-process execution within the web app

- Created ADR 0010 to outline the migration of Fuchs_DataService from a standalone service to an in-process library within the Fuchs web application.
- Updated configuration and logging management to be handled by the host application, streamlining the sync process.

Add publish profile and periodic hosted service for job scheduling

- Introduced a publish profile for deployment to a specified folder.
- Implemented PeriodicHostedService to manage multiple independent jobs, including the MFR ERP sync, with configurable execution intervals.

Add dotnet-tools.json for EF Core CLI tools

- Included dotnet-tools.json to manage the version of dotnet-ef for Entity Framework Core migrations and commands.

Fuchs/Views/Shared/_Layout.cshtml

@@ -19,6 +19,10 @@
     string appName  = ViewData["AppName"]  as string ?? "Fuchs Intranet";
     string fullName = ViewData["FullName"] as string ?? "";
     string pageTitle = ViewData["Title"] as string ?? "Intranet";
+    // When the deployment is flagged as a test/staging instance (Fuchs:IsTestDeployment = true),
+    // a distinctive green background is injected below so a test instance is never mistaken for
+    // production. Defaults to false (production) in appsettings.json.
+    bool isTestDeployment = Configuration.GetValue<bool>("Fuchs:IsTestDeployment");
     string? debugDbTarget = null;
     if (HostEnvironment.IsDevelopment())
     {
@@ -56,6 +60,15 @@
 
     @await RenderSectionAsync("CustomHeader", required: false)
 
+    @if (isTestDeployment)
+    {
+        <style>
+            body, html, body > header > nav, body > main > #topbar > nav {
+                background-color: #13a143 !important;
+            }
+        </style>
+    }
+
     <script type="text/javascript">
         $ocms.auth = @Html.Raw(JsonConvert.SerializeObject(authinfo));
     </script>