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/Docs/Concepts/live-draft-editing.md

@@ -1,4 +1,4 @@
----
+---
 status: Active
 lastUpdated: 2026-07-10
 applyTo:
@@ -55,13 +55,19 @@ Expiry:   Server (timer) --SignalR draftExpiring{token,secondsLeft}--> warn "bit
   exact editor JSON (`admin` / `new` / `req` blocks with `items`), plus server-computed
   `Sums`, `ValidationMessages`, `History`, `Version`, `Token`, `InvId`, `LastAccessUtc`.
 - **Calculation** (`InvoiceDraftCalculator`, static/pure) ports the former client math:
-  `RecomputeItem` (quantity × price × VAT, the `quantChange` port), `RecomputeTotals`
+  `RecomputeLineValues` (net/VAT/service-net/service-VAT per line from raw quantity ×
+  price × VAT rate, the `quantChange`/`setVat` port), `RecomputeTotals`
   (the `invSumUpdate`/`csms` aggregation + §13b reverse-charge), `RecomputePositions`
   (numbers every line except heading/free-text lines continuously across the whole invoice —
   mirroring the editor's `invSumUpdate`, so the editor and the PDF show identical `Pos.` numbers,
   including after a reorder),
   and `Validate` (email/address/items/VAT-rate/negative-total checks). Being pure, it is
-  exhaustively unit-tested.
+  exhaustively unit-tested. **The online editor performs no arithmetic of any kind** — not
+  header, footer, sums, totals, taxes, nor a single line's own net/VAT value: `$inv.quantChange`
+  and `$inv.setVat` only post the raw field the user changed (qty/price/vat rate), and
+  `$inv.invSumUpdate` only reassembles the row-contract array needed to post `req` — it computes
+  no totals, no VAT breakdown, and no service-refund note figures. All of those are rendered
+  exclusively from `dstate.sums` via `$inv.d.footer`.
 - **Sanitisation & reorder.** Scalar text deltas (`title`/`email`/`address`/`provisionperiod`/
   `provisionlocation`) and the section heading (`block.replace`) are stripped of the editor's
   TinyMCE HTML (`<p>…</p>`, `<br>`) to plain text in `ApplyDelta` (`HtmlToPlain`) — the backend
@@ -85,7 +91,8 @@ Expiry:   Server (timer) --SignalR draftExpiring{token,secondsLeft}--> warn "bit
   `draftClosed`. Business success/failure still flows through `IEventService`/`NotificationHub`.
 - **Frontend** (`$fis.draft` in `fis_main.js`, editor in `fis.inv_shared.js`) opens/joins,
   posts one delta per change, shows a loading state whenever awaiting a signal, and offers
-  "Änderungen verwerfen" and "Änderungshistorie" menu actions. It no longer computes totals.
+  "Änderungen verwerfen" and "Änderungshistorie" menu actions. It computes nothing — no
+  header, footer, sums, totals, taxes, or per-line values.
 
 ## Key files
 - `Fuchs/code/InvoiceDraftSession.cs` — session + `ChangeHistoryEntry` + `InvoiceDraftSums`.