Add units of measure and fractional quantities to rate lines

Quantities can now be time, count, distance, area, weight or volume, or a custom unit, instead of only
second/minute/hour/session/unit.

- Registry in src/lib/units.ts (mirrored in src-tauri/src/units.rs): grouped built-in units plus a custom unit of 1-12
  characters. A rate line's unit is validated when an invoice or a preset is saved; migration M12 drops the old unit
  allow-list from item_presets and keeps every row.
- Time is typed as h:mm: "4:30" hours counts as 4.5, "4:20" as 4.333... (kept exact, so rate x quantity rounds once, the
  same in TypeScript and Rust). Other units take plain decimals up to 3 places. A bad quantity blocks issuing.
- The PDF quantity column shows the unit ("4.5 hr", "12.75 km"); the rate keeps "per hour" / "/hr". RenderItem carries
  priceText, perText and rateShort, so no template parses the rate text with a regex over five hard-coded units.
- Quantity columns are sized from the widest word once a quantity with its unit is wider than 72 pt, so one long
  custom unit cannot squeeze the description (the serenity and citrus-split tables overflowed in the new fixture).
  Classic's quantity column is now content-sized.
- ERPNext: the default UOM map comes from the registry, with fractional-capable UOMs for time, distance, area, weight
  and volume. A custom unit is sent as Nos. A quantity that is not exact to 3 decimals (4:20 hours) is still refused for
  push, as before.
- Goldens and template thumbnails regenerated; the template harness has a "units" fixture with the longest texts.

Claude-Session: https://claude.ai/code/session_01PZypiWDfMkDTeEPeXjRhW5

src/pdf/templates/highlighter/plan.ts

@@ -1,6 +1,6 @@
 import type { ColSpec } from "../../engine/columns";
 import type { PageFrame } from "../../engine/geometry";
-import { drawnText, getMeasurer, measureToken } from "../../engine/measure";
+import { drawnText, getMeasurer, measureToken, wrapAwareTexts } from "../../engine/measure";
 import { textHeight, textLines } from "../../engine/textplan";
 import { fitSize } from "../../blocks/FitText";
 import { planItemsTable, type CellPart, type ItemsTablePlan, type TableCellValue } from "../../blocks/ItemsTable";
@@ -37,7 +37,7 @@ export function tableRows(model: RenderModel, v: HighlighterVariant, rateW: numb
   const r = v.roles;
   const hsn = Slot.HsnSac(model);
   return model.items.map((item, i) => {
-    const rate = rateCell(item.rateText, rateW, r.tableBody);
+    const rate = rateCell(item, rateW, r.tableBody);
     const rateParts: TableCellValue = typeof rate === "string" ? rate : ([rate[0], { text: rate[1], role: r.tableSub }] as CellPart[]);
     const desc: TableCellValue = hsn && slotHeights.hasHsn(hsn.values[i]) ? [...item.descriptionLines, { text: `${hsn.header}: ${hsn.values[i]}`, role: r.tableSub }] : item.descriptionLines;
     return [desc, item.qtyText, rateParts, item.amountText];
@@ -158,14 +158,14 @@ export function planHighlighter(model: RenderModel, frame: PageFrame, v: Highlig
   // --- table -----------------------------------------------------------------------------------------------------------------
   const t = v.table;
   const innerW = W - 2 * fr;
-  const rateOnly = model.items.map((i) => (i.rateText ? (/^(.*) per (second|minute|hour|session|unit)$/.exec(i.rateText)?.[1] ?? i.rateText) : "—"));
+  const rateOnly = model.items.map((i) => (i.priceText ?? "—"));
   const need = (texts: string[], head: string, pad: number) => Math.ceil(Math.max(0, ...texts.map((x) => measureToken(m, r.tableBody, x)), measureToken(m, r.tableHead, head))) + pad + v.hair + 6;
   const shortRate = model.items.map((i) => {
-    const cell = rateCell(i.rateText, 10000, r.tableBody);
+    const cell = rateCell(i, 10000, r.tableBody);
     return typeof cell === "string" ? cell : "—";
   });
   const cw = {
-    qty: Math.max(t.cols.qty, need(model.items.map((i) => i.qtyText), "Qty", 0)),
+    qty: Math.max(t.cols.qty, need(wrapAwareTexts(model.items.map((i) => i.qtyText), r.tableBody), "Qty", 0)),
     rate: Math.max(t.cols.rate, need(rateOnly, "Price", t.numPad), Math.min(t.cols.rate + 24, need(shortRate, "Price", t.numPad))),
     amount: Math.max(t.cols.amount, need(model.items.map((i) => i.amountText), "Total", t.numPad) - v.hair),
   };