fix: configurable handshake validity interval and improved defaults (#645)

* fix: support configurable rekey timeout interval for peer connectivity tracking (#641)

* change default check-time to 180s

docs/documentation/configuration/overview.md

@@ -28,6 +28,7 @@ core:
   
 backend:
   default: local
+  rekey_timeout_interval: 125s
   local_resolvconf_prefix: tun.
 
 advanced:
@@ -203,6 +204,13 @@ The current MikroTik backend is in **BETA** and may not support all features.
 - **Description:** The default backend to use for managing WireGuard interfaces. 
   Valid options are: `local`, or other backend id's configured in the `mikrotik` section.
 
+### `rekey_timeout_interval`
+- **Default:** `180s`
+- **Environment Variable:** `WG_PORTAL_BACKEND_REKEY_TIMEOUT_INTERVAL`
+- **Description:** The interval after which a WireGuard peer is considered disconnected if no handshake updates are received. 
+  This corresponds to the WireGuard rekey timeout setting of 120 seconds plus a 60-second buffer to account for latency or retry handling.
+  Uses Go duration format (e.g., `10s`, `1m`). If omitted, a default of 180 seconds is used.
+
 ### `local_resolvconf_prefix`
 - **Default:** `tun.`
 - **Environment Variable:** `WG_PORTAL_BACKEND_LOCAL_RESOLVCONF_PREFIX`