feat(dashboard): WG server tunnels show peer summary instead of per-peer rows

Server tunnels with many peers previously flooded the WG card. Now
server mode shows "X/Y peers online · ▼rx ▲tx" (3-min handshake
threshold) while client tunnels retain full per-peer detail.
Adds i18n keys dashboard.wgCard.peersOnline (EN/DE). v1.1.111.

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

management-ui/src/i18n/locales/en/common.json

@@ -734,7 +734,8 @@
     },
     "wgCard": {
       "title": "WireGuard",
-      "empty": "No WG tunnel configured yet."
+      "empty": "No WG tunnel configured yet.",
+      "peersOnline": "{{online}} / {{total}} peers online"
     },
     "firewallCard": {
       "title": "Firewall",