Standardize novu's discord server link throughout the codebase

Editor assessment

The subject is fully self-contained: one link, the Discord server URL, was standardized across the codebase, and a reader needs no diff to know exactly what happened and why it is desirable, consistent branding and fewer stale references. Chore is the accurate type; scope is absent but the sweep-everywhere phrasing makes that unimportant under the do-not-penalize guidance. No body is present and none is required for a change this mechanical. Hygiene is clean: imperative, no trailing period, no ticket junk, sensible length. A small message that does its one job completely, publishable as a tidy chore example.