docs: update README for v0.11.7 Beta — all new features documented

Added sections for: Device Tags, Availability Tracking, Network Topology
improvements (LLDP-authoritative, manual links, orphan detection), Device
Network Tools table (Ping/Traceroute/IP Scan/WoL/Packet Capture/Bandwidth
Test), Scheduled Backups, Maintenance Windows, Audit Log, Configuration
Templates, and TOTP 2FA. Alert delivery channels listed. Project structure
updated to note audit middleware. Version bumped to 0.11.7 Beta.

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mikrotik-manager-backend",
-  "version": "0.11.6-beta",
+  "version": "0.11.7-beta",
   "description": "Mikrotik Network Management Platform - Backend API",
   "main": "dist/index.js",
   "scripts": {