fix: multi-node online stats, per-node Hy2 ports, and panel reload stability

Co-authored-by: Cursor <cursoragent@cursor.com>

panel/db.py

@@ -6,7 +6,7 @@ import hmac
 import os
 import secrets
 import sqlite3
-import subprocess
+import uuid
 from pathlib import Path
 
 ROOT = Path(os.environ.get("JIEDIAN_ROOT", Path(__file__).resolve().parents[1]))
@@ -156,6 +156,4 @@ def node_count() -> int:
 
 
 def _generate_credentials() -> tuple[str, str]:
-    uuid = subprocess.check_output(["sing-box", "generate", "uuid"], text=True).strip()
-    hy2 = secrets.token_urlsafe(18)[:24]
-    return uuid, hy2
+    return str(uuid.uuid4()), secrets.token_urlsafe(18)[:24]