feat: add share modal with visibility picker and link management

Create ShareModal component with three-tier visibility picker
(private/link/public), share link creation with configurable expiration,
clipboard copy, and link revocation. Wire into setup detail page
replacing the static visibility badge with an interactive share button.

Plan: 32-03 (Setup Sharing System - Share Modal UI)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/hooks/useShares.ts

@@ -0,0 +1,42 @@
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import { apiDelete, apiGet, apiPost } from "../lib/api";
+
+interface ShareLink {
+	id: number;
+	setupId: number;
+	token: string;
+	permission: string;
+	expiresAt: string | null;
+	createdAt: string;
+	revokedAt: string | null;
+}
+
+export function useShareLinks(setupId: number | null) {
+	return useQuery({
+		queryKey: ["shares", setupId],
+		queryFn: () => apiGet<ShareLink[]>(`/api/setups/${setupId}/shares`),
+		enabled: !!setupId,
+	});
+}
+
+export function useCreateShareLink(setupId: number) {
+	const queryClient = useQueryClient();
+	return useMutation({
+		mutationFn: (data: { expiresInDays: number | null }) =>
+			apiPost<ShareLink>(`/api/setups/${setupId}/shares`, data),
+		onSuccess: () => {
+			queryClient.invalidateQueries({ queryKey: ["shares", setupId] });
+		},
+	});
+}
+
+export function useRevokeShareLink(setupId: number) {
+	const queryClient = useQueryClient();
+	return useMutation({
+		mutationFn: (shareId: number) =>
+			apiDelete<ShareLink>(`/api/setups/${setupId}/shares/${shareId}`),
+		onSuccess: () => {
+			queryClient.invalidateQueries({ queryKey: ["shares", setupId] });
+		},
+	});
+}