feat: show RDP session duration in Overview and Events (0.5.16)

Add session_duration_sec to EventSummary and a Duration column (HH:MM:SS / Nd HH:MM:SS).

backend/app/services/telegram_templates.py

@@ -564,9 +564,11 @@ def _format_rdg_html(event: Event) -> str:
     err = _detail(details, "gateway_error_code", "error_code", default="")
     if err != "-":
         msg += _line("⚠️", "Код ошибки", html_escape(err))
-    dur = _detail(details, "session_duration_sec", default="")
-    if dur not in ("-", "0", ""):
-        msg += _line("⏱️", "Длительность", f"{html_escape(dur)} с")
+    from app.services.session_duration import extract_session_duration_sec, format_session_duration
+
+    dur_sec = extract_session_duration_sec(details if isinstance(details, dict) else None)
+    if dur_sec is not None and dur_sec > 0:
+        msg += _line("⏱️", "Длительность", html_escape(format_session_duration(dur_sec)))
     msg += _line("🕐", "Время", format_time(event.occurred_at))
     win_id = _detail(details, "event_id_windows", default="")
     if win_id != "-":