Add toasts, Settings tabs, Clients page and item presets (Phase E1)

- Global Carbon toast stack replaces scattered inline notices; errors persist until closed.
- Settings is split into eight tabs with one Save and a remembered last tab; Numbering embeds the series settings.
- New Clients page with a DataTable, shared add/edit modal, structured addresses, GST category (informational), per-client notes and payment terms. The composed address string is kept for back-compat. Deleting a client warns about invoice count; issued invoices keep their own snapshot.
- Migration M7 adds the client columns and item_presets; existing clients with a GSTIN are backfilled to registered_regular.
- New invoice form: client ComboBox with type-ahead and inline create, client defaults applied on selection, and an Add from preset control.
- Rust tests for M7 (fresh and v6 upgrade), client validation and CRUD, presets CRUD; vitest for the toast store and new helpers.

PDF output and fingerprint goldens are unchanged. The new UI has not been run in a webview yet.

src/views/InvoiceHistory.tsx

@@ -2,7 +2,6 @@ import { useEffect, useState } from "react";
 import {
   Button,
   InlineLoading,
-  InlineNotification,
   Modal,
   OverflowMenu,
   OverflowMenuItem,
@@ -24,17 +23,17 @@ import type { ExportMode } from "../lib/filename";
 import { useInvoiceExport } from "../hooks/useInvoiceExport";
 import ExportFeedback from "../components/ExportFeedback";
 import type { InvoiceSummary, Settings } from "../lib/types";
+import { useToast } from "../components/ToastProvider";
 
 export default function InvoiceHistory({ settings, active }: { settings: Settings; active: boolean }) {
+  const toast = useToast();
   const [rows, setRows] = useState<InvoiceSummary[]>([]);
   const [loading, setLoading] = useState(true);
-  const [error, setError] = useState<string | null>(null);
   const [busyId, setBusyId] = useState<number | null>(null);
   const [cancelTarget, setCancelTarget] = useState<InvoiceSummary | null>(null);
   const [reason, setReason] = useState("");
   // Whether each invoice has an archived PDF; unknown (absent) until its status was read.
   const [archived, setArchived] = useState<Record<number, boolean>>({});
-  const [notice, setNotice] = useState<string | null>(null);
   const exp = useInvoiceExport({
     settings,
     bank: null,
@@ -44,9 +43,8 @@ export default function InvoiceHistory({ settings, active }: { settings: Setting
   const load = async () => {
     try {
       setRows(await api.listInvoices());
-      setError(null);
     } catch (e) {
-      setError(String(e));
+      toast.error("Could not load invoices", String(e));
     } finally {
       setLoading(false);
     }
@@ -78,14 +76,12 @@ export default function InvoiceHistory({ settings, active }: { settings: Setting
 
   const onExport = async (id: number, mode: ExportMode, source: ExportSource) => {
     setBusyId(id);
-    setError(null);
-    setNotice(null);
     try {
       // Fetched now, not at list time: the row summary does not carry the archive fields.
       const invoice = await api.getInvoice(id);
       await exp.start(invoice, mode, source);
     } catch (e) {
-      setError(String(e));
+      toast.error("Export failed", String(e));
     } finally {
       setBusyId(null);
     }
@@ -93,19 +89,17 @@ export default function InvoiceHistory({ settings, active }: { settings: Setting
 
   const onArchive = async (id: number) => {
     setBusyId(id);
-    setError(null);
-    setNotice(null);
     try {
       const invoice = await api.getInvoice(id);
       const outcome = await renderAndArchive(invoice, createExportDeps({ settings, bank: null }));
       if (outcome.archived) {
         setArchived((a) => ({ ...a, [id]: true }));
-        setNotice(`Invoice ${invoice.number} is archived.`);
+        toast.success(`Invoice ${invoice.number} is archived`);
       } else {
-        setError(`Invoice ${invoice.number}: ${outcome.error ?? "the PDF could not be archived."}`);
+        toast.error("Could not archive the PDF", `Invoice ${invoice.number}: ${outcome.error ?? "the PDF could not be archived."}`);
       }
     } catch (e) {
-      setError(String(e));
+      toast.error("Could not archive the PDF", String(e));
     } finally {
       setBusyId(null);
     }
@@ -115,12 +109,13 @@ export default function InvoiceHistory({ settings, active }: { settings: Setting
     if (!cancelTarget) return;
     try {
       await api.cancelInvoice(cancelTarget.id, reason);
+      toast.success(`Invoice ${cancelTarget.number} cancelled`);
       setCancelTarget(null);
       setReason("");
       await load();
     } catch (e) {
       setCancelTarget(null);
-      setError(String(e));
+      toast.error("Could not cancel the invoice", String(e));
     }
   };
 
@@ -129,11 +124,6 @@ export default function InvoiceHistory({ settings, active }: { settings: Setting
       <h1 className="voiced-page__title">Invoices</h1>
       <p className="voiced-page__subtitle">Every invoice you have issued, newest first.</p>
 
-      {error ? (
-        <InlineNotification kind="error" lowContrast title="Something went wrong" subtitle={error} />
-      ) : null}
-
-      {notice ? <InlineNotification kind="success" lowContrast title={notice} onCloseButtonClick={() => setNotice(null)} /> : null}
       <ExportFeedback exp={exp} />
 
       {loading ? (