Add Zabbix API token authentication support

ZABBIX_API_TOKEN env var can now be used instead of ZABBIX_USER +
ZABBIX_PASSWORD. When set, the token is passed directly as the auth
value in JSON-RPC calls and no login/logout session is created.

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

docker-compose.yml

@@ -28,8 +28,11 @@ services:
 
       # ── Zabbix API (optional) ─────────────────────────────────────────────
       # Leave ZABBIX_URL empty to disable automatic host management.
-      # Requires Zabbix 6.0+.
-      ZABBIX_URL: "https://monitor.stranto.com"              # e.g. "http://zabbix.example.com"
+      # Requires Zabbix 5.4+.
+      ZABBIX_URL: "https://monitor.stranto.com"
+      # Use an API token (preferred) OR user + password — not both.
+      # Create token in Zabbix: Administration → API tokens → Create API token
+      ZABBIX_API_TOKEN: ""
       ZABBIX_USER: "odmon"
       ZABBIX_PASSWORD: "lk09u834ojnaslvnjh09u34g"
       ZABBIX_HOST_GROUP: "Yodeck Players"