Add payments with TDS, invoice detail view and filterable History (Phase E2)

- Migration M8 adds payments (cash, TDS, mode, reference). Payment status is derived, never stored: unpaid, partially paid, paid, or overdue. Overpayment is rejected, TDS counts toward settling, and only issued invoices accept payments. list_invoices and get_invoice carry the paid, TDS and balance summary.
- New invoice detail view: archived-PDF preview, payments list, Record payment modal, Export, Duplicate (as a draft), Re-render and Cancel. An invoice with payments cannot be cancelled until they are deleted.
- History gets search, status, financial-year, month and client filters, sortable columns, pagination, footer totals and an FY summary. Cancelled invoices are excluded from totals. The per-row archive-status calls are gone; archiving is on the detail page.
- Rust tests for payments and the list summary; vitest for fiscal-year, money, filter and duplicate helpers.

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

src/lib/money.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+import { formatPaise, paiseToInput, parseRupeesToPaise } from "./money";
+
+describe("money", () => {
+  it("parses typed amounts to exact paise", () => {
+    expect(parseRupeesToPaise("1250.5")).toBe(125050);
+    expect(parseRupeesToPaise("1,25,000")).toBe(12500000);
+    expect(parseRupeesToPaise("₹ 99.99")).toBe(9999);
+    expect(parseRupeesToPaise("0.29")).toBe(29);
+    expect(parseRupeesToPaise("19.9")).toBe(1990);
+    expect(parseRupeesToPaise("5.")).toBe(500);
+    expect(parseRupeesToPaise("")).toBe(0);
+  });
+
+  it("rejects non-amounts", () => {
+    for (const bad of ["abc", "-5", "1.234", "1e3", "1.2.3", ".5"]) expect(parseRupeesToPaise(bad)).toBeNull();
+    expect(parseRupeesToPaise("99999999999999999999")).toBeNull();
+  });
+
+  it("formats", () => {
+    expect(paiseToInput(123450)).toBe("1234.50");
+    expect(paiseToInput(5)).toBe("0.05");
+    expect(formatPaise(12500000)).toBe("₹1,25,000.00");
+  });
+});