Fix ticket_id never stored when fail_thresh>1; guard sessionStorage JSON.parse

monitor.py: _ticket_interface/_ticket_unifi/_ticket_unreachable all used
`if tid and is_new` to guard db.set_ticket_id(). Since is_new is True only
on the first upsert (consec=1) but tickets are created at consec>=fail_thresh
(default 2), is_new is always False when the ticket is created, so the
ticket link never appeared in the UI. Changed to `if tid:`.

links.html: JSON.parse(sessionStorage.getItem(...)) in togglePanel and
restoreCollapseState had no try-catch. Corrupt/stale session storage would
throw an uncaught SyntaxError. Also wrapped all sessionStorage.setItem
calls in try-catch to defend against storage-full / private-browsing errors.

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

monitor.py

@@ -789,7 +789,7 @@ class NetworkMonitor:
             f'Please inspect the cable/SFP/switch port for {host}/{iface}.'
         )
         tid = self.tickets.create(title, desc, priority='2')
-        if tid and is_new:
+        if tid:
             db.set_ticket_id(event_id, tid)
 
     # ------------------------------------------------------------------
@@ -831,7 +831,7 @@ class NetworkMonitor:
             f'Please check power and cable connectivity.'
         )
         tid = self.tickets.create(title, desc, priority='2')
-        if tid and is_new:
+        if tid:
             db.set_ticket_id(event_id, tid)
 
     # ------------------------------------------------------------------
@@ -873,7 +873,7 @@ class NetworkMonitor:
             f'Please check the host power, management interface, and network connectivity.'
         )
         tid = self.tickets.create(title, desc, priority='2')
-        if tid and is_new:
+        if tid:
             db.set_ticket_id(event_id, tid)
 
     # ------------------------------------------------------------------