fix: use Set.size, show short keys in startup log

server.js

@@ -26,7 +26,8 @@ const BKN = (() => {
 })();
 
 function maskKey(k) {
-  if (!k || k.length < 12) return "***";
+  if (!k) return "(empty)";
+  if (k.length <= 12) return k;
   return k.slice(0, 6) + "..." + k.slice(-4);
 }
 
@@ -1448,7 +1449,7 @@ http.createServer(router).listen(PORT, HOST, () => {
   console.log("");
   console.log("==================================================");
   console.log(`[STARTUP] Listening on http://${HOST}:${PORT}`);
-  console.log(`[STARTUP] API keys: ${API_KEYS.length} (source: ${process.env.IMA_API_KEYS ? "env" : "config"})`);
+  console.log(`[STARTUP] API keys: ${API_KEYS.size} (source: ${process.env.IMA_API_KEYS ? "env" : "config"})`);
   for (const k of API_KEYS) console.log(`[STARTUP]   key: ${maskKey(k)} (len=${k.length})`);
   console.log("==================================================");
   console.log("");