Initial commit: Voiced invoice desktop app

Offline-first invoicing app for Test Vendor, built by Bongbetic.

- Tauri v2 (Rust) + React/TypeScript + IBM Carbon Design System UI
- SQLite (rusqlite) storage with a persistent invoice-number series
- Guided first-run setup, pre-filled vendor/bank details
- Fixed-amount or rate x quantity line items (per sec/min/hour/session/unit)
- GST as CGST+SGST or IGST, Indian amount-in-words
- Optional signature, with a computer-generated note as fallback
- Print-ready PDF export via @react-pdf/renderer
- Windows cross-compile via cargo-xwin (NSIS installer)

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>

src/components/AppShell.tsx

@@ -0,0 +1,69 @@
+import {
+  Content,
+  Header,
+  HeaderGlobalAction,
+  HeaderGlobalBar,
+  HeaderMenuItem,
+  HeaderName,
+  HeaderNavigation,
+  SkipToContent,
+} from "@carbon/react";
+import { Asleep, Light } from "@carbon/icons-react";
+import type { ReactNode } from "react";
+
+export type AppView = "new" | "invoices" | "series" | "settings";
+
+const NAV: { id: AppView; label: string }[] = [
+  { id: "new", label: "New invoice" },
+  { id: "invoices", label: "Invoices" },
+  { id: "series", label: "Series" },
+  { id: "settings", label: "Settings" },
+];
+
+interface AppShellProps {
+  view: AppView;
+  onNavigate: (view: AppView) => void;
+  theme: string;
+  onToggleTheme: () => void;
+  children: ReactNode;
+}
+
+export function AppShell({ view, onNavigate, theme, onToggleTheme, children }: AppShellProps) {
+  const wordmark =
+    theme === "g100" ? "/brand/bongbetic-wordmark-light.png" : "/brand/bongbetic-wordmark-dark.png";
+
+  return (
+    <>
+      <Header aria-label="Voiced">
+        <SkipToContent />
+        <HeaderName href="#" prefix="">
+          <span className="voiced-brand">
+            <img className="voiced-brand__logo" src={wordmark} alt="Bongbetic" />
+            <span className="voiced-brand__divider" aria-hidden="true" />
+            <span className="voiced-brand__product">Voiced</span>
+          </span>
+        </HeaderName>
+        <HeaderNavigation aria-label="Voiced navigation">
+          {NAV.map((item) => (
+            <HeaderMenuItem
+              key={item.id}
+              isCurrentPage={view === item.id}
+              onClick={(event) => {
+                event.preventDefault();
+                onNavigate(item.id);
+              }}
+            >
+              {item.label}
+            </HeaderMenuItem>
+          ))}
+        </HeaderNavigation>
+        <HeaderGlobalBar>
+          <HeaderGlobalAction aria-label="Toggle colour theme" onClick={onToggleTheme}>
+            {theme === "g100" ? <Light size={20} /> : <Asleep size={20} />}
+          </HeaderGlobalAction>
+        </HeaderGlobalBar>
+      </Header>
+      <Content id="main-content">{children}</Content>
+    </>
+  );
+}