feat(07-02): add weight unit toggle and wire all formatWeight call sites

- Add segmented g/oz/lb/kg toggle to TotalsBar with settings persistence
- Pass unit parameter to all 8 formatWeight call sites across components and routes
- Import useWeightUnit hook in ItemCard, CandidateCard, CategoryHeader, SetupCard, ItemPicker, Dashboard, SetupDetail

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/client/components/ItemPicker.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useState } from "react";
 import { useItems } from "../hooks/useItems";
 import { useSyncSetupItems } from "../hooks/useSetups";
+import { useWeightUnit } from "../hooks/useWeightUnit";
 import { formatPrice, formatWeight } from "../lib/formatters";
 import { LucideIcon } from "../lib/iconData";
 import { SlideOutPanel } from "./SlideOutPanel";
@@ -20,6 +21,7 @@ export function ItemPicker({
 }: ItemPickerProps) {
 	const { data: items } = useItems();
 	const syncItems = useSyncSetupItems(setupId);
+	const unit = useWeightUnit();
 	const [selectedIds, setSelectedIds] = useState<Set<number>>(new Set());
 
 	// Reset selected IDs when panel opens
@@ -114,7 +116,7 @@ export function ItemPicker({
 												</span>
 												<span className="text-xs text-gray-400 shrink-0">
 													{item.weightGrams != null &&
-														formatWeight(item.weightGrams)}
+														formatWeight(item.weightGrams, unit)}
 													{item.weightGrams != null &&
 														item.priceCents != null &&
 														" · "}