feat(i18n): extract strings from navigation, dialogs, onboarding, settings, and login

- Add useTranslation() to TopNav, BottomTabBar, FabMenu, UserMenu
- Internationalize ConfirmDialog, AuthPromptModal, ExternalLinkDialog
- Extract all onboarding flow strings (Welcome, HobbyPicker, ItemBrowser, Review, Done)
- Internationalize settings page (weight unit, currency, API keys, import/export)
- Internationalize login page and root error boundary
- All dialogs in __root.tsx use t() for UI chrome

Phase 34, Plan 02 (core navigation and global UI)

src/client/components/onboarding/OnboardingItemBrowser.tsx

@@ -1,4 +1,5 @@
 import { getTagsForHobbies } from "@/shared/hobbyConfig";
+import { useTranslation } from "react-i18next";
 import { usePopularItems } from "../../hooks/useOnboarding";
 import { SelectableItemCard } from "./SelectableItemCard";
 
@@ -17,6 +18,7 @@ export function OnboardingItemBrowser({
 	onContinue,
 	onSkip,
 }: OnboardingItemBrowserProps) {
+	const { t } = useTranslation("onboarding");
 	const tags = getTagsForHobbies(selectedHobbies);
 	const { data: items, isLoading } = usePopularItems(tags);
 
@@ -48,11 +50,12 @@ export function OnboardingItemBrowser({
 		<div className="flex flex-col items-center min-h-screen px-8 py-16">
 			<div className="max-w-5xl w-full text-center">
 				<h1 className="text-3xl font-bold text-gray-900 mb-2">
-					Popular gear for{" "}
-					{selectedHobbies.length === 1 ? selectedHobbies[0] : "your hobbies"}
+					{selectedHobbies.length === 1
+						? t("items.title", { hobby: selectedHobbies[0] })
+						: t("items.titleMultiple")}
 				</h1>
 				<p className="text-base text-gray-500 mb-8">
-					Tap items you already own. We'll add them to your collection.
+					{t("items.subtitle")}
 				</p>
 
 				{isLoading && (
@@ -64,11 +67,10 @@ export function OnboardingItemBrowser({
 				{!isLoading && !hasItems && (
 					<div className="py-12 text-center">
 						<h2 className="text-lg font-semibold text-gray-900 mb-2">
-							No gear cataloged yet
+							{t("items.noCatalog")}
 						</h2>
 						<p className="text-base text-gray-500 mb-8">
-							We're still building our catalog for this hobby. You can skip this
-							step and add gear manually later.
+							{t("items.noCatalogDescription")}
 						</p>
 					</div>
 				)}
@@ -105,8 +107,7 @@ export function OnboardingItemBrowser({
 							onClick={onContinue}
 							className="px-8 py-3 bg-gray-700 hover:bg-gray-800 text-white font-medium rounded-lg transition-colors"
 						>
-							Review {selectedItemIds.size}{" "}
-							{selectedItemIds.size === 1 ? "item" : "items"}
+							{t("items.reviewCount", { count: selectedItemIds.size })}
 						</button>
 					)}
 					<button
@@ -114,7 +115,7 @@ export function OnboardingItemBrowser({
 						onClick={onSkip}
 						className="text-sm text-gray-400 hover:text-gray-600 transition-colors"
 					>
-						Skip this step
+						{t("common:actions.skipStep")}
 					</button>
 				</div>
 			</div>