fix(backend): SSE subscribe substr, Zod issues, users param - #606

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/checkout@v4, github/codeql-action/analyze@v3, github/codeql-action/autobuild@v3, github/codeql-action/init@v3. Actions will be forced to run with Node.js 24 by default starting June 16th, 2026. Node.js 20 will be removed from the runner on September 16th, 2026. Please check if updated versions of these actions are available that support Node.js 24. To opt into Node.js 24 now, set the FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true environment variable on the runner or in your workflow file. Once Node.js 24 becomes the default, you can temporarily opt out by setting ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION=true. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

1 issue was detected with this workflow: CodeQL language 'javascript' is referenced by more than one entry in the 'language' matrix parameter for job 'codeql-analysis'. This may result in duplicate alerts. Please edit the 'language' matrix parameter to keep only one of the following: 'javascript', 'typescript'.