feat(po): add week, month, year to line-item unit options

The PO line-items Unit of Measure dropdown only offered hr/day among
time-based units. Add week, month and year so durations beyond days can
be selected, as requested. UOM_OPTIONS is the single source of truth and
`unit` is validated as a free-form string, so no schema/validation change
is needed.

Fixes #44

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

App/components/po/po-line-items-editor.tsx

@@ -20,8 +20,11 @@ const UOM_OPTIONS = [
   { value: "mL",   label: "mL — Millilitre" },
   { value: "m",    label: "m — Metre" },
   { value: "m2",   label: "m² — Sq. Metre" },
-  { value: "hr",   label: "hr — Hour" },
-  { value: "day",  label: "day — Day" },
+  { value: "hr",    label: "hr — Hour" },
+  { value: "day",   label: "day — Day" },
+  { value: "week",  label: "week — Week" },
+  { value: "month", label: "month — Month" },
+  { value: "year",  label: "year — Year" },
   { value: "lump", label: "lump — Lump Sum" },
   { value: "Ltr",  label: "Ltr — Litre (alt)" },
 ];

App/tests/unit/po-line-items-editor.test.tsx

@@ -93,6 +93,25 @@ describe("LineItemsEditor — edit mode", () => {
     const lastCall = onChange.mock.calls[onChange.mock.calls.length - 1][0] as LineItemInput[];
     expect(lastCall[0].gstRate).toBeCloseTo(0.05);
   });
+
+  it("offers month and year as unit-of-measure options", () => {
+    render(<LineItemsEditor items={[DEFAULT_ITEM]} onChange={vi.fn()} />);
+    const selects = screen.getAllByRole("combobox") as HTMLSelectElement[];
+    const unitSelect = selects.find((s) => s.value === "pc")!;
+    const values = Array.from(unitSelect.options).map((o) => o.value);
+    expect(values).toContain("month");
+    expect(values).toContain("year");
+  });
+
+  it("calls onChange with the selected duration unit", async () => {
+    const onChange = vi.fn();
+    render(<LineItemsEditor items={[DEFAULT_ITEM]} onChange={onChange} />);
+    const selects = screen.getAllByRole("combobox") as HTMLSelectElement[];
+    const unitSelect = selects.find((s) => s.value === "pc")!;
+    fireEvent.change(unitSelect, { target: { value: "year" } });
+    const lastCall = onChange.mock.calls[onChange.mock.calls.length - 1][0] as LineItemInput[];
+    expect(lastCall[0].unit).toBe("year");
+  });
 });
 
 // ── Totals calculation (edit mode) ────────────────────────────────────────────