Add the ERPNext settings UI, History and detail controls, and voiced.invoice.v1 export (Phase F3)

- Settings gets an Integrations tab: connection fields with a write-only API secret, a CA PEM option, Test connection with versions and warnings, live mapping lists loaded after a test, naming mode, toggles and its own Save.
- Pushing for a GST-registered vendor is refused until a connection test result is stored. The UI shows the reason and disables Send.
- History shows an ERPNext status column from one bulk call, a row Send and Open in ERPNext, and a bulk Send selected with a draft-or-submit confirm step and per-row results that never abort the batch. The detail view gets an ERPNext panel and per-payment send. All of it is hidden or disabled when the integration is not configured.
- Optional auto-push after issue runs in the background and never blocks or fails the issue.
- Generic export: a deterministic voiced.invoice.v1 JSON (and CSV line items) for selected invoices, documented in docs/voiced-invoice-v1.md with a golden test. Money is integer paise plus a decimal string.

The new screens have not been run in a webview yet. The ERPNext Payment Entry deduction fields still need a live check.

src/lib/settingsTab.ts

@@ -9,6 +9,7 @@ export const SETTINGS_TABS = [
   { id: "templates", label: "Templates & export" },
   { id: "fonts", label: "Fonts" },
   { id: "data", label: "Data" },
+  { id: "integrations", label: "Integrations" },
 ] as const;
 
 export type SettingsTabId = (typeof SETTINGS_TABS)[number]["id"];
@@ -19,8 +20,21 @@ export function parseSettingsTab(value: string | null | undefined): number {
   return index < 0 ? 0 : index;
 }
 
+/** A tab another screen asked for; used once by the next Settings mount, so it works without localStorage. */
+let requested: SettingsTabId | null = null;
+
+/** Makes the next opening of Settings land on `id` (for "Set up in Settings" links). */
+export function requestSettingsTab(id: SettingsTabId): void {
+  requested = id;
+}
+
 /** The last Settings tab this viewer used. A per-viewer convenience only. */
 export function loadSettingsTab(): number {
+  if (requested) {
+    const index = parseSettingsTab(requested);
+    requested = null;
+    return index;
+  }
   try {
     return parseSettingsTab(localStorage.getItem(KEY));
   } catch {