Fix PHP 8.4 breakage: drop deprecated mysqli::ping(), harden dep handler

The hosts were upgraded to PHP 8.4, where mysqli::ping() is deprecated
(auto-reconnect was removed in 8.2). Database::getConnection() called it on
every reused connection, and api/ticket_dependencies.php's custom error
handler treated the deprecation as a fatal 500 ('A server error occurred'),
breaking the ticket Dependencies tab.

- Database.php: remove the redundant ping()/reconnect check (connection is
  request-scoped; no liveness check needed on PHP 8.2+).
- ticket_dependencies.php: only abort on genuine errors; log notices/
  warnings/deprecations and continue, so a future deprecation can't 500 it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

helpers/Database.php

@@ -22,11 +22,9 @@ class Database
             self::$connection = self::createConnection();
         }
 
-        // Check if connection is still alive
-        if (!self::$connection->ping()) {
-            self::$connection = self::createConnection();
-        }
-
+        // Note: no ping()/reconnect check — mysqli auto-reconnect was removed in
+        // PHP 8.2 and mysqli::ping() is deprecated in 8.4. The connection is
+        // request-scoped and short-lived, so a liveness check is unnecessary.
         return self::$connection;
     }