AI Gateway credentials gain endpoint instance URL

The editor canvas gets a visual polish pass while AI Gateway credentials gain a configurable endpoint instance URL for flexible deployment scenarios.
This patch release addresses two distinct improvements across the n8n platform.
In the editor, sub-node icons are now properly centered on the canvas, and triggers panel icons refresh more reliably. These are small UI corrections that add up to a more polished workflow-building experience.
More significantly, AI Gateway credentials can now specify an endpoint instance URL. This gives teams running distributed or air-gapped n8n deployments the flexibility to point their AI integrations at specific gateway endpoints rather than relying on a single hardcoded destination.
The changes span the editor UI and the credentials system, with version bumps across the monorepo's root package, CLI, and frontend editor packages.