refactor: Code cleanup and documentation updates

Bug fixes:
- Fix ticket ID extraction using URLSearchParams instead of split()
- Add error handling for query result in get_users.php
- Make Discord webhook URLs dynamic (use HTTP_HOST)

Code cleanup:
- Remove debug console.log statements from dashboard.js and ticket.js
- Add getTicketIdFromUrl() helper function to both JS files

Documentation:
- Update Claude.md: fix web server (nginx not Apache), add new notes
- Update README.md: add keyboard shortcuts, update setup instructions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

api/get_users.php

@@ -37,6 +37,10 @@ try {
     $sql = "SELECT user_id, username, display_name FROM users ORDER BY display_name, username";
     $result = $conn->query($sql);
 
+    if (!$result) {
+        throw new Exception("Failed to query users");
+    }
+
     $users = [];
     while ($row = $result->fetch_assoc()) {
         $users[] = [