Quick-win fixes from second review

- create_ticket_api.php: validate status (against TICKET_STATUSES) and
  priority (numeric 1-5). A non-numeric priority previously cast to 0 and
  escalated the ticket below P1 on the dedup/update path.
- manage_workflows.php: reject empty/invalid from_status/to_status on POST
  and PUT (must be valid ticket statuses) so the workflow table can't be
  populated with bogus transitions.
- TicketModel::getAllTickets: COUNT(*) OVER() rides on returned rows, so a
  page past the last row returned total/pages = 0. Fall back to a direct
  COUNT when an over-range page yields no rows, keeping pager math correct.
- DashboardView: stop double-escaping category/type/assigned active-filter
  labels (they were htmlspecialchars'd into the label and again at output,
  rendering R&D as R&D); output escaping is retained.
- check_duplicates.php / NotificationHelper::notifyWatchers: wrap the DB
  lookups in try/catch so a failed prepare/query degrades gracefully
  (advisory dup-check returns none; best-effort watcher notify is skipped)
  instead of fataling the request. Works whether mysqli throws or returns
  false. (manage_* endpoints already have a top-level try/catch.)

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

models/TicketModel.php

@@ -208,6 +208,11 @@ class TicketModel
                 ORDER BY $sortExpression $sortDirection
                 LIMIT ? OFFSET ?";
 
+        // Keep a copy of the filter params (without LIMIT/OFFSET) for the
+        // fallback COUNT below.
+        $countParams    = $params;
+        $countParamTypes = $paramTypes;
+
         $params[] = $limit;
         $params[] = $offset;
         $paramTypes .= 'ii';
@@ -228,6 +233,24 @@ class TicketModel
         }
         $stmt->close();
 
+        // COUNT(*) OVER() rides on returned rows, so a page past the last row
+        // yields zero rows and a bogus total of 0. Fall back to a direct COUNT
+        // so the total/pages stay correct for stale or over-range page links.
+        if ($totalTickets === 0 && $offset > 0) {
+            $countSql = "SELECT COUNT(*) AS c
+                         FROM tickets t
+                         LEFT JOIN users u_created ON t.created_by = u_created.user_id
+                         LEFT JOIN users u_assigned ON t.assigned_to = u_assigned.user_id
+                         $whereClause";
+            $countStmt = $this->conn->prepare($countSql);
+            if (!empty($countParams)) {
+                $countStmt->bind_param($countParamTypes, ...$countParams);
+            }
+            $countStmt->execute();
+            $totalTickets = (int)($countStmt->get_result()->fetch_assoc()['c'] ?? 0);
+            $countStmt->close();
+        }
+
         return [
             'tickets' => $tickets,
             'total' => $totalTickets,