feat(gui): add reverse DNS hostname detection for peers

Resolve hostname via PTR record on peer endpoint IP.
Results cached in memory for 5 minutes to avoid latency.
Hostname shown below endpoint in the peers table.

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

gui/app.py

@@ -197,6 +197,27 @@ def humanize_ago(ts: int, now: int) -> str:
     return f"{diff // 86400}д назад"
 
 
+_dns_cache: dict = {}  # ip -> (hostname, expires_ts)
+_DNS_TTL = 300  # 5 минут
+
+
+def resolve_hostname(ip: str) -> str:
+    if not ip or ip in ("-", "(none)"):
+        return ""
+    now = time.time()
+    if ip in _dns_cache:
+        host, exp = _dns_cache[ip]
+        if now < exp:
+            return host
+    import socket
+    try:
+        host = socket.gethostbyaddr(ip)[0]
+    except Exception:
+        host = ""
+    _dns_cache[ip] = (host, now + _DNS_TTL)
+    return host
+
+
 def next_free_ip(network: str) -> str:
     import ipaddress
     try:
@@ -297,6 +318,7 @@ def index():
                 "routes": row.get("advertised_routes") or "-",
                 "allowed_ips": rt.get("allowed_ips", "-"),
                 "endpoint": rt.get("endpoint", "-"),
+                "hostname": resolve_hostname(rt.get("endpoint", "").split(":")[0]),
                 "handshake_ago": humanize_ago(ts, now),
                 "rx": bytes_h(rt.get("rx_bytes", 0)),
                 "tx": bytes_h(rt.get("tx_bytes", 0)),
@@ -337,6 +359,7 @@ def index():
                 "routes": imported_routes,
                 "allowed_ips": rt.get("allowed_ips", "-"),
                 "endpoint": rt.get("endpoint", "-"),
+                "hostname": resolve_hostname(rt.get("endpoint", "").split(":")[0]),
                 "handshake_ago": humanize_ago(ts, now),
                 "rx": bytes_h(rt.get("rx_bytes", 0)),
                 "tx": bytes_h(rt.get("tx_bytes", 0)),