feat: add signup disable config and fix telemetry startup

[mox56]

Title

Add disable_user_signup config and fix telemetry startup crash

Summary

This PR adds a server-side disable_user_signup flag to block new account creation and temporary guest sessions, and also fixes a startup crash in backend telemetry caused by a mismatched OpenTelemetry runtime import.

Releated Issues

Closes issue#3260
Closes issue#3314

What changed

• Added disable_user_signup to config types, defaults, and self-hosting docs.
• Blocked fresh signup and temp-user creation when the flag is enabled.
• Blocked fresh OIDC account creation under the same flag.
• Exposed the flag to the GUI shell and /whoarewe so the frontend can hide signup and skip guest creation.
• Fixed telemetry initialization by switching from type-only Resource usage to resourceFromAttributes(...).
• Rebuilt the backend output so startup no longer crashes on resources_1 is not defined.

Verification

• Backend auth/homepage/system/OIDC tests pass.
• npm run build:ts passes.
• npm start no longer hits the resources_1 crash during prestart/build.

Note To Reviewers

This is my first contribution to a project. I appreciate any feedback or suggestions for improvement.

[CLAassistant]

All committers have signed the CLA.

[xsourabhsharma]

looks goods to me