Refactor code structure and remove redundant sections for improved readability and maintainability

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

@@ -51,9 +51,22 @@ Expiry:   Server (timer) --SignalR draftExpiring{token,secondsLeft}--> warn "bit
   `Sums`, `ValidationMessages`, `History`, `Version`, `Token`, `InvId`, `LastAccessUtc`.
 - **Calculation** (`InvoiceDraftCalculator`, static/pure) ports the former client math:
   `RecomputeItem` (quantity × price × VAT, the `quantChange` port), `RecomputeTotals`
-  (the `invSumUpdate`/`csms` aggregation + §13b reverse-charge), and `Validate`
-  (email/address/items/VAT-rate/negative-total checks). Being pure, it is exhaustively
-  unit-tested.
+  (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.
+- **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
+  is the single source of truth, so no HTML reaches the DB, the PDF or a reloaded draft. Section
+  drags post a `block.order` delta (`["id",…]`) that reorders `Req`; positions are then
+  renumbered and pushed back via the view state (`applyState`/`applyPositions`). The change
+  history records the **changed field** (e.g. the new heading text), never the whole block JSON.
+  The PDF (`FuchsPdf`) renders a heading row per block (`FdsInvoiceData.InvoiceBlocks`) and shows
+  every position's price (set members are priced like standalone lines; only `setonly` collapses
+  them), so the PDF preview mirrors the online editor.
 - **Orchestration** (`InvoiceDraftEditService`, scoped) opens sessions (from a fresh
   payload or by reloading a DB draft via `fds__getInvoice`, reshaped like
   `BuildInvoiceRequestList`), applies deltas (`ApplyDelta`), builds the view-state DTO,