feat: multi-server failover, health monitor, port hopping

- client/phobos-health.sh: router-side health monitor + auto-heal
  - Cron every 60s, checks WG handshake age
  - Auto-restart obfuscator (3min), WireGuard (5min)
  - Port hopping (10min), server failover (15min)
  - Auto-return to primary when recovered
- client/failover.conf.example: multi-server config template
- server/secondary-setup.sh: one-command secondary server deploy
  - WG + multi-port obfuscator + mini-API on :8444
  - Auto-registers with main server
- Panel: new "Серверы" page
  - Add/remove secondary servers
  - Health check, peer sync, fetch info
  - API key management
  - Secondary server install command

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/failover.conf.example

@@ -0,0 +1,15 @@
+# Phobos Failover Configuration
+# Format: SERVER_N=host:port1,port2,port3
+# KEY_N=obfuscation_key_for_server_N
+
+# Primary server (main, with web panel)
+SERVER_1=144.124.252.104:51821,51822,51823
+KEY_1=Fc3X8GbVQD2FuHPbOjKiaP83nWSwNojJ
+
+# Secondary server (backup, VPN only)
+# SERVER_2=backup.example.com:51821,51822
+# KEY_2=backup_obfuscation_key_here
+
+# Emergency server (last resort)
+# SERVER_3=emergency.example.com:43210
+# KEY_3=emergency_key_here