feat: add default furni icon repair sources

Fall back to well-known public furni icon hosts (HabboAssets, Hubbly,
Leet) when no clone sources are configured, so Repair Icons can download
missing icons out of the box. Also handle variant classnames (base name
and '*' replaced with '_') and extract icons from remote .nitro bundles.
Send a browser User-Agent on downloads to avoid being blocked by hotels.

src/lib/services/import/core/download.ts

@@ -29,7 +29,14 @@ export async function downloadFile(
 			if (attempt > 0) {
 				await new Promise((r) => setTimeout(r, baseDelay * 2 ** (attempt - 1)));
 			}
-			const res = await fetch(url, { signal: AbortSignal.timeout(15000) });
+			const res = await fetch(url, {
+				signal: AbortSignal.timeout(15000),
+				headers: {
+					"User-Agent":
+						"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0 Safari/537.36",
+					Accept: "image/png,image/*,*/*;q=0.8",
+				},
+			});
 			if (!res.ok) {
 				const deterministic =
 					res.status === 404 || res.status === 410 || res.status === 403;