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>

helpers/NotificationHelper.php

@@ -164,32 +164,38 @@ class NotificationHelper
             return;
         }
 
-        // Fetch watcher usernames, excluding the actor so they don't notify themselves
-        if ($excludeUserId !== null) {
-            $sql  = "SELECT u.username FROM ticket_watchers tw JOIN users u ON tw.user_id = u.user_id WHERE tw.ticket_id = ? AND tw.user_id != ?";
-            $stmt = $conn->prepare($sql);
-        } else {
-            $sql  = "SELECT u.username FROM ticket_watchers tw JOIN users u ON tw.user_id = u.user_id WHERE tw.ticket_id = ?";
-            $stmt = $conn->prepare($sql);
-        }
-        // Notifications are best-effort; if the watchers table is absent or the
-        // statement fails to prepare, skip silently rather than fataling the
-        // request that already committed its DB change.
-        if (!$stmt) {
-            return;
-        }
-        if ($excludeUserId !== null) {
-            $stmt->bind_param("ii", $ticketId, $excludeUserId);
-        } else {
-            $stmt->bind_param("i", $ticketId);
-        }
-        $stmt->execute();
-        $result = $stmt->get_result();
-        $stmt->close();
-
+        // Fetch watcher usernames, excluding the actor so they don't notify
+        // themselves. Notifications are best-effort: if the watchers table is
+        // absent or the query fails, skip silently rather than fataling the
+        // request that already committed its DB change. mysqli may either throw
+        // (default exception mode) or return false, so handle both.
         $usernames = [];
-        while ($row = $result->fetch_assoc()) {
-            $usernames[] = $row['username'];
+        try {
+            if ($excludeUserId !== null) {
+                $sql  = "SELECT u.username FROM ticket_watchers tw JOIN users u ON tw.user_id = u.user_id WHERE tw.ticket_id = ? AND tw.user_id != ?";
+                $stmt = $conn->prepare($sql);
+            } else {
+                $sql  = "SELECT u.username FROM ticket_watchers tw JOIN users u ON tw.user_id = u.user_id WHERE tw.ticket_id = ?";
+                $stmt = $conn->prepare($sql);
+            }
+            if (!$stmt) {
+                return;
+            }
+            if ($excludeUserId !== null) {
+                $stmt->bind_param("ii", $ticketId, $excludeUserId);
+            } else {
+                $stmt->bind_param("i", $ticketId);
+            }
+            $stmt->execute();
+            $result = $stmt->get_result();
+            $stmt->close();
+
+            while ($row = $result->fetch_assoc()) {
+                $usernames[] = $row['username'];
+            }
+        } catch (\Throwable $e) {
+            error_log('NotificationHelper::notifyWatchers watcher lookup failed: ' . $e->getMessage());
+            return;
         }
 
         if (empty($usernames)) {